ERDAS IMAGINE TUTORIAL .PDF
ERDAS Imagine is a frequently used software package within the Remote .. All three of these can be automatic or manual, in practice the manual option. Crop mapping using remote sensing data of Landsat 8: A Training Manual. . ERDAS Imagine is a powerful software package that is used (by remote sensing. 3 | ERDAS IMAGINE The world's most widely-used remote sensing software package. ERDAS IMAGINE. Geographic imaging professionals need to process.
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The ERDAS IMAGINE Tour Guides manual is part of a whole suite of printed and on- ERDAS Spatial Modeler Language Reference Manual (only as zetom.info). Preface. About This Manual The ERDAS IMAGINE Essentials Tour Guides™ manual is a documents, digital hardcopy documents which are delivered as PDF. Three modules presented in this tutorial will guide users through the process of .. for an ERDAS IMAGINE file,.jpg for JPEG,.jp2 for JPEG ,.png for PNG.
The effect is especially important for space borne sensors of high spatial resolution. The scattering is caused by molecules as well as aerosols in the atmosphere.. Richter Vertical path from sea level to space. This adjacency effect diminishes the image contrast and causes a certain amount of blurring. Atmospheric correction is especially useful when comparing multitemporal scenes.
Changes in scenes recorded at different times thus correspond to actual changes on the earth's surface and not to changes caused by different atmospheric conditions.
Erdas Imagine User Manual
The atmosphere modifies the information of the earth's surface in several ways: For surface temperatures close to the air temperature the emissivity effect on the retrieved temperature is even less since a reduction in the surface emitted radiation is nearly compensated for by an increase in the reflected downwelling atmospheric flux. The retrieval of ground temperature from remotely sensed radiance measurements generally requires multi-band thermal sensors and some information about the surface emissivity.
A rule of thumb is that a 1 per cent emissivity shift leads to a 0. Barton Especially in urban areas.
Temperature results can be checked if the scene contains calibration targets. ATCOR2 In the years to There may still be discrepancies between the temperature of the upper water surface layer measured by a radiometer and the bulk water temperature a few centimeters below the surface. Since TM collects only single-band thermal data.
Cloud areas have to be masked to exclude them from haze areas and to enable a successful haze removal. The surface temperatures of curves 2 and 3 are close together if the surface temperature is not much higher than the air temperature.
In this case if no atmospheric correction is applied curve 1. The optical thickness of cloud areas is so high that the ground surfaces cannot be seen. The above figure demonstrates the improvement gained with atmospheric correction in the thermal region. Cloud shadow regions are currently not identified. As a first approximation. Curve 3 corresponds to a surface emissivity of 0. Curve 1 is the at-satellite blackbody temperature no atmospheric correction.
It can be estimated and removed as described below. Midlatitude summer atmosphere. The cloud mask is coded with 1. For bands below nm the histograms are calculated for each HOT level j.
The dehazed new digital number is see figure on next page: The current implementation provides a mask for haze-over-land coded with Haze areas are orthogonal to the "clear line".
It consists of five major steps: Calculation of the histogram of HOT for the haze areas. Two options are available: Masking of clear and hazy areas with the tasseled cap haze transformation Crist and Cicone The algorithm only works for land pixels. The clear area pixels are taken as those pixels where TC is less than the mean value of TC. If no blue band exists.
It is a combination of the improved methods of Richter b and Zhang et al. Masking of clear and hazy areas: Histogram HOT: If only limited clear areas are available within the image predominantly clouds and haze the algorithm fails. The visibility range is 5. US standard atmosphere 3. Visibilities ranged from 5 to 40 km. Currently the following atmospheres are available: Richter and Lehmann.
Landsat TM. MOMS Kaufmann et al. The edition comprises ground elevations from 0 to 2. For a wide range of atmospheric conditions and solar zenith angles this database enables the conversion of raw data gray levels into ground reflectance images and ground brightness temperature data thermal band.
Kalyanaraman et al. Values in between are linearly interpolated. The atmospheric correction functions are stored as look-up tables in the database and consist of the following parameters: The edition of the database increased the range of ground elevations to 1.
Ground elevations ranged from 0 to 1 km above sea level. The atmospheric correction functions were calculated for Landsat TM..
Kneizys et al. For sensors without tilt capability the radiative transfer calculation is performed for the nadir view.. The calculation is performed for the elevations 0.
It decreases with increasing wavelength and visibility. The atmospheric correction functions also depend on the sensor view angle. The transmittance functions are the direct beam and diffuse transmittances from the ground to the sensor.
The path radiance is calculated for 7 relative angles of Azimuth 0 to deg. In both dimensions. This is done for a 10 deg wide mesh of tilt angles. In this way. The results were calculated for a standard midlatitude summer atmosphere with a rural aerosol at three visibilities for a ground at sea level. The following figure shows a graphic presentation of the course of some selected atmospheric correction functions for Landsat TM band 2.
Elevations in between are obtained by interpolation. Path radiance and diffuse solar flux on the ground decrease with increasing visibility. Function q is a measure of the strength of the scattering efficiency adjacency effect.
The Longitude and Latitude can be entered as dd: Both entries are automatically converted to decimal values. L 22 The Time of Day can be entered as: This option calculates the Solar zenith degrees and the Solar azimuth degrees for your image.
If desired it also could be edited manually. In this case a backup file will be created. Open an existing ATCOR2 project will open a file chooser menu and let you select your existing project file. Create a new ATCOR2 project will open a file chooser menu and let you define your new project file name. Value Adding VAP: Option to derive value adding products such as leaf area index LAI.
Output Raster File. Sensor Type. Solar Zenith and Ground Elevation. Input Layers. Calibration File. Tab 1: Specifications in this Tab all file and sensor parameters have to be specified Input Raster File. This module is described in the last section of this manual.
Scale Factors. Acquisition Date. Tab 2: Atmospheric Selections in this Tab all parameters concerning the atmospheric conditions at the time of the data acquisition have to be specified. Run Correction: The Acquisition Year is included for documentation purposes only. Extensive tests have shown that even with a bilinear resampling technique the spectral consistency is maintained and ATCOR will yield good results.
The Acquisition Day of the image is used to correct for the actual earth. Data type: Only data of 8-bit U8 unsigned and bit U16 unsigned are allowed. Otherwise an error message will appear. For further details also check chapter 7. TM band 6 is the thermal band. The sequence of bands is arbitrary for all modules. TM band 3 might be the first band of the input file. L Note: In general it is not recommended to edit the original sequence of bands. Some sensors require specific entries: The first number is the layer-number of the input file.
In order to process the HG-band you need to remove band 6 LG from the input data and place the HG band usually on last position on the original data CD at this position. TM band 7 is the 2. These Output Scale Factors are used to scale the output reflectance image. This depends on the sensor as listed below.
Since the output image is encoded like the input image 1 byte per pixel for most sensors. L 13 as Layer 10 6 LG or HG as Layer 6 Panchromatic images can nevertheless also be atmospherically corrected a haze removal is not possible. The same principle is used to encode the ground brightness temperature degree Celsius, TM band 6 data and ASTER band 13 only using Factor for temperature fctem and Offset for temperature offtem for negative Celsius temperatures.
The correct sensor has to be selected from the pull-down listing. Only sensors which have the same number of bands or more bands as the input file are allowed. Otherwise an error message: The correct calibration file has to be selected from a file chooser listing:. Some sensors have specific files e. These are dedicated calibration files for the provided test data. Frequently updated information for calibration files will be available from this site.
With the option Calculate… the Sun-position Calculator Chapter 5. In case the Solar Zenith is not known it can be calculated with this tool. Apply… automatically imports the value into the Menu. These values can be found in the Meta Data for the selected image.
Solar Azimuth: Sensor Tilt: Satellite Azimuth:. Practically speaking, it is the ease with which features along the skyline can be distinguished from the sky itself. This again is influenced by Extinction: The Visibility Estimate… function provides a visibility value for the selected aerosol type by checking dark scene pixels in the red band vegetation, water and NIR band water.
It is assumed that the lowest reflectance in the red band is 0. Therefore, the obtained visibility value usually can be considered as a lower bound. The aerosol content of the atmosphere at a given location will depend on the trajectory of the local air mass during the preceding several days.
This aerosol consists of dust-like and organic particles. This is done in two steps. This step can be skipped if a Haze Removal only is intended! This also holds for polar. In these areas. In forested. If these values and the correct gains have been selected. L Negative values in the measured spectra: In principle reflectance can not have a negative value. The selected values will later be used in the atmospheric correction module. This module works with the originally recorded gray level image.
Its purpose is the determination of an appropriate atmosphere aerosol and humidity and the decision on the selected visibility ground meteorological range. L NOTE: If a Haze Removal only is intended. In the output reflectance image the pixel with negative values are set to zero. For sensors with a thermal band if it has been included in the Layer-Band-Assignment option the ground brightness temperature can be calculated. The aerosol type is in general quite insensitive rural works quite well in most cases as well as the humidity default: The resulting two spectra will show the influence and facilitate a decision on the appropriate calibration.
This usually happens in dark targets water or dark vegetation. Also a visibility of approximately 30km is usually a good starter. It calculates and displays a box-averaged reflectance spectrum based on the selected calibration file. Clicking with the within one of the images will display the spectrum in the selected reflectance charts Chart 1 or Chart 2: Main Display Setup The image is displayed automatically in two windows the Band Selection is done according to the Viewer Preferences for all images: Both can be used to pick a spectrum.
L When initially displayed.. If one of the set parameters gain. Within this first tab of the SPECTRA Control Menu most of the parameters which had already been selected earlier can again be modified to study their effect on the spectrum: The parameter K0 has a default value for the following sensors it usually does not have to be changed: In this case use the Scale.
Box Size: Target Box Size Pixels: There you can update the original calibration file Path: It is still open in the background. A backup file will be generated automatically. Since the DN values of the pixels on every surface always differ a little from each other. By pressing the Save last spectrum button the user can save the last picked reflectance spectrum in a file. The default value of this box is 5. If the adjacency effect should be switched off.
A new menu is opened. The outer box is just an indicator to identify the picked target easier it is not the adjacency area [see next paragraph].
All digital number DN values of each layer inside this box will be averaged. Range of Adjacency Effect m the adjacency effect is taken into account in the computation of the reflectance for the spectral graphs. Only odd numbers are allowed to be entered in this number field.
The target box can be different for each picked target. To do this.
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By default. There are two different possibilities to save information into a file at this point. The user can specify the filename. To be able to view the saved data with the SpecView tool. It is recommended to produce such a file when all the parameters that will be used for the atmospheric correction are chosen. Counting starts from 1 again if this "save" option was used. The next table contains the information available with the option "Save multiple spectra".
Three pine targets: The adult leaves or needles. This spectrum is displayed in red color. Original Spectra: Reference Spectra Description agrisoil. The branches are produced in regular "pseudowhorls".
For this reason they can only be deleted by pressing "Clear" for that chart. Therefore it is not possible to delete the last target spectrum before a reference spectrum. Reference spectra are not displayed in the table above each chart.
Its wavelength range and the number of wavelength entries have to agree with the wavelength channels of the selected sensor. Load Reference Spectrum: A reference spectrum. A maximum of 2 reference spectra may be picked for display inside each chart. To be able to draw a reference spectrum in a chart. The bark of most pines is thick and scaly. Also there always has to be at least one target spectrum in the list legend before a reference spectrum. Spruce etym.: Spruces are large trees, from 95 m tall when mature, and can be distinguished by their whorled branches and conical form.
The needles, or leaves, of spruce trees are attached singly to the branches in a spiral fashion, each needle on a small peg-like structure called a pulvinus. Resampled Spectra: These spectra are also available resampled to the spectral bands of the supported sensors. The corresponding filenames consist of the original filename with a two character sensor tag. Since these data are tailored to each sensor they can be displayed as reference plots in the ATCOR2 reflectance charts.
The Resampled Spectra option is the preferred option at the start of a project. The main objective in comparing the measured spectra and a reference spectra is not to get an exact fit by changing e. User Data User-supplied reference spectra may be included in any directory and displayed in the chart viewers. The users are advised to build their own spectral libraries, using the possibilities given inside this ATCOR2 module.
Usersupplied reference spectra may be included in the ". Background for the AutoCalibration Function: For the atmospheric and topographic correction of satellite data ATCOR needs true radiances at the sensor aperture.
The actual digital number DN or gray level imagery delivered by satellite data providers, usually is not radiance L data. A simple linear relationship has to be employed to convert the DN into L: The band specific radiometric calibration values c0, c1 are stored in ATCOR calibration files for each supported sensor.
As a starter, the ATCOR calibration files contain values which are either pre-flight values or values which have been provided by the satellite data vendors. In principle, for a optimal result, a specific calibration file should be created for each image which is being processed using the parameters of the meta data or being provided by the data vendor. This can then be used during the following processing steps:.
With this selection the target can be selected. A target is a area for which a measured reference spectrum is available. Click on the button and use the left mouse button to select a reference target. With this step the signature or spectrum of a known surface the reference must be selected.
Name the new calibration file Confirm to use the new calibration file in the subsequent processing. Select a reference spectrum from the examples. It is possible to create your own spectra by editing an existing one be careful with the formatting.
The examples spectra are located in.. For e. For the correct identifiers check the following table: L To verify the parameters defining the atmospheric conditions previously selected in the main ATCOR menu, it is now possible to select the same target with the standard SPECTRA procedures and display the target plus the spectra selected for the calibration target in one of the reflectance charts. The Auto-Calibration algorithm uses the currently set parameters for visibility and the atmospheric model to calculate the c0 and c1 values used in the calibration files.
After having determined an optimal set of parameters aerosol type. The important parameters for atmospheric correction are: TM bands 4 to 7 This information is seldom available for the date and time of image data acquisition. An incorrect aerosol type will cause very low reflectance values. The aerosol type with the best performance should be selected to continue with the next step to vary the visibility.
Possible candidates are water and vegetation. Click-on this target in the image to display its spectrum for the three main aerosol types urban. Compare these reflectance values with the following tables. Iterations to get to meaningful atmospheric conditions: The decision criterion should be a consistent trend in the spectra of different targets. Target Blue 0. This may be based on local nearby weather stations or climatologic charts. The humidity range is dry to very humid: A quick pre-view processing DeHaze Preview should be selected first if the image is relatively large and the trial and error approach selecting the correct parameters would be time rather consuming.
The DeHaze Preview is a standard de-hazing operation performed on a degraded image to fit the output window. If the option Perform Haze Removal before Correction? It is suggested to leave the initial default after installation it is a Cloud Threshold.
A performance meter will show the status of the degradation process. The Correction report gives for e. DeHaze Preview. The Constant Atmosphere Module menu has an option on the left side. There is a 3rd Threshold for snow. With this option the threshold for the cloud mask can interactively be controlled.
Only if the resulting water mask is not correct. The range is 1 — The default value is a 3. It is suggested to leave the initial default after installation it is a 9. The current implementation provides a mask for hazeover-land coded with The last option is the choice in most cases. The activation depends on the size of the input image. If the image does not have a NIR-Band an error message will appear.
The range is 10 — If used. Only if the resulting cloud mask is not correct. The range is 2 — The status line explains where it stands and simultaneously the Correction Report is filled with information: Options in the above Menu: It has the default name: This file is also accessible in the output directory as: This option displays the haze-mask which was used in the detection of haze vs.
Inquire Cursor…. It is used during the haze reduction process. Additionally the pixels detected as clouds or snow are shown in blue. It shows the detected haze as gray levels. Fit Image to Window and Geo. Additionally a haze-levels file is produced. Arrange Layers. The algorithm is not suitable for haze over water. An example is shown below: The method can also be used for data without the blue band but will yield less perfect results. The following Error Message will appear for the described error conditions: The correction report gives all information concerning the haze calculation.
X Not Selected! The method needs clear and hazy areas. The progress can be seen in the status line. There will be no further questions asked. The correction report gives all information concerning the atmospheric processing. It is written into the output directory where the output file resides.
The file is actually written in the moment the Constant Atmosphere Window is closed again. A report file is automatically produced. Only the derivation of the Haze-Mask is influenced by the calibration file. All Sensors supported can be selected. Also all the Options of Tab-1 and -2 within the ATCOR Main Menu which deal with setting the atmospheric condition at the time of the data take do not need to be elaborated in detail.
Only the adjacency effect might be compensated and e. The effect of an atmospheric correction is -as no haze removal is done. External Models can not be incorporated.
Available from local Meteorological-Data. Detailed values can be extracted from meta-data of the satellite scene or the data provider. Available in the Meta-Data of the Satellite Scene. A Haze removal is not possible as no bands for an estimation of the haze are available. Available in the Meta-Data of the Satellite Scene or set individually. For rugged terrain a correction might be worth while as ATCOR3 as well compensates for a topographic effect shadow removal.
It already contains all necessary parameters. Processing Parameters Report File: This example is also available after installation on your PC where it is installed if chosen during installation in the directory: Date of Acquisition: Solar zenith angle: Germany x pixel August The scene contains haze and a cloud region. Since the temperature derivation is based on a surface emissivity of 0. Sutherland The emissivity of vegetation and soil in the Results for some selected surface cover types are: The figure on the following page shows spectra taken from the corrected image.
Although no comparison with ground truth reflectance spectra is available. The visibility mask left image on the next page is clearly displaying the haze regions. A surface brightness temperature map is calculated from the thermal band of TM. Visibility Mask.
Reflectance spectra of the TM scene. Brightness Temperature Map. The following sections contain some tips about the selection of the atmosphere and sensor calibration files. The atmosphere closest to the measured or assumed conditions of the scene to be processed should be selected. The effect of a degradation in the instrument sensitivity is a decrease of the recorded radiance. It assumes horizontal surfaces of Lambertian reflectance.
Price Results of radiative transfer calculations are stored in a database of look-up tables. Slater et al. A discussion on the sensor calibration files is also included. The next two sections contain tips concerning the choice of the appropriate atmosphere and aerosol from the database.
Some numerical results are given elsewhere Kaufman and Sendra A file with the results of the latest in-flight calibration may easily be added to the existing calibration files. The limitations of the algorithm are: It is well known that the sensitivity of optical space sensors changes with time. It neglects the scan angle dependence of the radiance and transmittance functions.
The reduced optical depth will result in a smaller atmospheric correction. Data of the thermal band of Landsat TM are converted into a ground brightness temperature image. The advantages of the implemented algorithm are: Usually this assumption will not have a strong effect on the correction Lee and Kaufman SPOT band 3 show a moderate dependence of the measured signal on the water vapor content.
Data of TM bands 1. TM bands 4. Together with the background aerosol of more or less pronounced continental character they form a fairly uniform maritime aerosol which is representative in the lowest 2. So updated calibration files may be included with time. One reason is that different radiative transfer codes can yield slightly different radiances. Nominal values of these coefficients for each band i are given in the appropriate calibration files extension ". Data of all bands of sensors in the 0.
A second reason is that different ground receiving stations use different processing algorithms and processing techniques may change. Last but not least the sensitivity of instruments may change with time. These aerosols are largely sea-salt particles which are produced by the evaporation of sea-spray droplets.
Since the suppliers of satellite images deliver calibration information in various units it is important to stick to the radiance unit employed in ATCOR. Calibration coefficients from literature may differ slightly. SPOT bands 1 and 2 are almost not influenced by the water vapor content of the atmosphere. A second possibility -if no values are available. For Landsat 1. One possibility is to check the ancillary information of the original data for updated values www.
The solar geometry is specified with the solar elevation and azimuth angle. Radiometric Parameters: The metadata is specified in two files. The bias c 0 i corresponds to the dark current Markham et al. The standard offset values are zero. It will be updated with time when inflight calibration results are available. Geometric Parameters: Besides the atmospheric LUTs for the nadir view. Occasionally however.
The first file is intended for a quick overview. DIM file. Nearly all SPOT data DIM and can be found when the file is opened with an editor. SPOT orbit geometry In addition to the tilt angle the view direction with respect to the flight path is specified. Solar and view geometry Attention: For this old format the SPOT leader file and the voldir.
This is a header coding error. LISS-2A etc. The IRS calibration coefficients c 0 i. Information on the radiometric calibration coefficients should be available from the Indian Space Research Organization or IRS data distributors. The offset c0 values are 0. Only imagery products without DRA retain radiometric accuracy. This results in the following cal-file e. This is done by rescaling the raw digital data transmitted from the satellite. Calibration coefficients from Space Imaging [SI]: As 11bit data do not 'exist' they will be already in bit U Nominal Collection Azimuth: The N-S direction.
And you also should use the bit cal-files. The Nominal Collection Azimuth is the angle between 1. The line connecting the target point and the satellite's projection on the target point's horizon tangent plane and.
The direction of this angle is always clockwise. Nominal Collection Elevation: The Nominal Collection Elevation is the angle between 1st the target point's horizon tangent plane and. Value taken from Table 2 This leads to the following equation for c1 for QuickBird data: The paper is not available any more on the digitlaglobe.
This tech note discusses the conversion from a corrected counts QuickBird product to top-of-atmosphere spectral radiance.
As can be seen in the above mentioned document the offset c0 is 0 for QuickBird. IMD File A. In this case. Products Generated After T Products Generated Before T IMD files are the revised factors and should be used for radiance conversion. These factors look like: Product Guide. DN Option Min-Max. In this case no stretching would have to be performed.
Layerstack with the VNIR. The atmosphere closest to the measured or assumed water vapor profile for the current scene should be selected. The fall. Only the lower 5 km altitudes are shown. The tables are intended to guide the user in the selection of the appropriate atmosphere. The following tables are ordered according to an increasing water vapor content. The reflective and thermal spectral region are treated separately. The model-derived planetary albedo is given below eq. Atm indicates the dependence on atmospheric parameters.
An upper limit of the range of this effect is about 2. If the measured planetary albedo equation 9. Since the strength of the adjacency effect depends on the reflectance differences of neighboring fields. The appropriate effective range can iteratively be determined: If the range is too small the central lake area will have higher retrieved reflectance values e. In cases of high atmospheric scattering efficiency.
Landsat TM: In the NIR spectral region R is about 0. Evaluating eq. In the thermal spectral region.
Since the adjacency effect is a second order effect. The exact relationship for the reflected radiance of equation 9. If the default option of adjacency correction is accepted. E g is the global direct plus diffuse solar flux on the ground for a zero reflectance ground. A discussion of the error bounds due to the small angle approximation is given elsewhere Richter For acrosstrack tilt sensors like SPOT two relative azimuth angles.
For a wide range of atmospheric conditions and solar zenith angles. The atmospheric database contains the necessary path radiance. For nadirlooking sensors the atmospheric correction functions are evaluated for the nadir view angle. This means the sensor.
For the omnidirectional tilt sensor Quick Bird four relative azimuth angles are provided: The second term of equation 9.
E th thermal downwelling flux on the ground.. The path radiance for view angles between nadir and the maximum off-nadir view angle are calculated with linear interpolation. A separate investigation showed that the relative reflectance errors increase with increasing solar zenith angle.
Richter a. The errors also decrease with rising surface reflectance. The solar zenith angle has to be specified for the image corners and a bilinear interpolation is applied to determine the sun angle for each pixel. In addition. Gillespie et al. The spectral band index is omitted for brevity. It may increase to 0.
The advantage of the proposed classification approach is that it also works for instruments with only a single thermal band such as Landsat-5 TM. In cases of multispectral thermal bands and when the emissivity spectrum is of interest. For the same visibility the difference between the aerosol types rural. Several possibilities exist to address this problem Gillespie et al.
The corresponding errors are less than 0. T and the spectral channel response: The influence due to the neglection of the scan angle dependence is usually less than 0.
Three surface cover classes are currently employed: T2 and increment e. This value is based on a classification of the previously calculated surface reflectance spectrum of each pixel. In this case the output image is scaled as 16 bit integer and negative surface temperatures fit in the data range. Another possibility is to use a scale factor of 10 or higher for the reflectance and temperature data. In Digital Airborne Spectrometer Experiment.. Air Force Research Laboratory.. JPL-Publication Hanscom MA SP p.
Water Resources Research.. Remote Sensing of Environment. New York. Remote Sens. Remote Sensing of Environment.. An algorithm for de-shadowing spectral imagery. Journal of Geophysical Research. Netherlands Remote Sensing. IEEE Trans. JPL Publ. IEEE Trans Applied Optics.
Solar Energy. In Proc. Part II. Geophysical Research.. Technical note RS TN radiometric radiance Digital Globe Geoscience and Remote Sensing USA Applied Meteorology.. Rotterdam Applied Optics..
CO Elsevier Academic Press. Part 1: CA The Palette options described below will apply in this case. This option will generate a relatively small output file, at the expense of some color fidelity depending on the palette that you choose.
The image data will be compressed using the PackBits compression algorithm. GeoTIFF images generated with this option will be at least 3 times the size of those generated with the 8-bit Palette option, but the colors in the image will exactly match what you see on the screen. GeoTIFF images generated with this option will maintain good color fidelity and often be highly compressed, although they will lose some information as compared to the uncompressed bit RGB option.
s Arc coverages and shapefiles
This will generate by far the smallest image, but if you source image had more than two colors the resulting image will be very poor. By default, white will be a value of 0 and black will be a value of 1, but you can reverse this by selecint the Grayscale - Min Is Black palette option.
Elevation samples will be stored as signed bit integers. There are only a handful of software packages that can recognize a vertical GeoTIFF properly, so only use this if you know it works. Elevation samples will be stored as bit floating point values. When generating a color 8-bits per pixel GeoTIFF, it is necessary to select a palette indicates what colors will be used to describe the image being exported. This option will generate the best results, but can more than double the export time required if any high color images are present in the export set.
If all of the input data is palette-based and the combined palette of those files has colors or less, then the combined files of the input file will just be used with no additional export time being required. The palette consists of only the standard DRG colors. The palette consists of the 14 standard DRG colors with the remaining colors being a range of gray values ranging from black to white.
This palette is the best choice when exporting anything but DRGs and grayscale satellite photos. You can save a. Black will be stored as zero with varying shades of gray up to white with a value of White will be stored as zero with varying shades of gray up to black with a value of The Vertical Units field allows the user to select the vertical units to use when exporting elevation data i. Any input data not in the selected vertical units will be automatically converted on export.
The default value is the average of the grid spacings of all the currently loaded raster and elevation overlays. If the Always Generate Square Pixels option is checked, the smaller of the specified x and y resolutions will be used Table of Contents 27 Global Mapper - User's Manual for both the x and y resolution.
Forcing square pixels ensures that the resultant GeoTIFF file will look good even in software that is not able to deal with pixels that aren't square. Some software, in particular graphics editing software, makes use of this value when sizing TIFF files for printout. If the Interpolate to Fill Small Gaps in Data option is checked, any small areas with missing data will be filled in by interpolating the surrounding valid data. This is useful for filling small gaps between adjacent tiles or small holes in elevation data.
This generally results in the best compression for TIFF files, but is not yet supported by all software applications. If the application s that you are going to be using the TIFF file with supports LZW, using this compression method is definitely suggested. Note that this will create a larger file and not all applications will support TIFF files with alpha channels.
The Global Mapper Grid format is a highly compressed elevation grid format that loads and draws very quickly and requires very little memory. If you have a choice for what format to store your gridded elevation data in, we suggest using the Global Mapper Grid format. When selected, the command displays the Global Mapper Grid Export Options dialog which allows the user to setup the export.Sandmeier and Itten If the measured planetary albedo equation 9.
The offset c0 values are 0. Iterations Looping. Correction of atmospheric and topographic effects for high spatial resolution satellite imagery..
Water vapour partial pressure as a function of air temperature and humidity. ATCOR2 9.