8 votes

Creating a Time series NDVI map

When remote sensing vegetation, the time of year is very important. In most climates, vegetation has significantly more biomass (i.e., leaves etc.) during the summer, which means that it is easier for ...
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6 votes

Remove clumps of pixels in R

Thanks to @gene and https://geoscripting-wur.github.io/AdvancedRasterAnalysis/ I can now answer my question (copied and modified): library(raster) # create some raster data r <- raster(ncols=12, ...
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  • 3,224
6 votes

Confidence in pan-sharpened classification?

In general, there are two approaches to classification: pixel-based and object-based: Pixel-based: Each spatial pixel is evaluated by itself against a set classification parameters. In this case, ...
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5 votes

Digital Number (DN) on satellite imagery?

You need to provide more details! There are many "satellite's". If the data is 0-255 it is 8-bit and represents DN. In a processing workflow some analyst prefer to scale floating-point to 16-bit so, ...
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5 votes

Creating a Time series NDVI map

Reproducing the map example you provided is primarily a cartographic effort and requires very little analysis if you have already calculated NDVI. I would use the following workflow to produce the ...
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  • 50.2k
5 votes

Using sieve filter in ERDAS Imagine and/or ArcGIS for Desktop?

The sieve model is fairly straight forward and you can implement it in ArcGIS using "RegionGroup", "ExtractByAttributes", "SetNull" and "Nibble". It is good to understand how these methods actually ...
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5 votes
Accepted

Erdas python scripting help

A good documentation can be found here (.pdf). Also look at the Erdas forum here. Another good resource is ERDAS IMAGINE 2014 Python Examples
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5 votes

Matching colours in already mosaiced single image?

The image needs to be cut apart and re-mosaiced after adjusting the colors in each piece. This can be done. As an example, I extracted the green band of the image. To make my work simple (the ...
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  • 67.5k
5 votes
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How to easily identify/classify coniferous forest from one date Landsat image?

NDVI is for vegetation/non vegetation discrimination. So if your vegetation is always coniferous forest, then it should be the most efficient method in your case. Otherwise you will have confusions ...
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  • 48.5k
4 votes
Accepted

Looking for simple software to compare two Landsat Images

I have not tried it but Opticks is worth a shot: http://opticks.org/confluence/display/opticks/Welcome+To+Opticks
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4 votes
Accepted

Imagine files between ERDAS and ENVI

ENVI has never been very good with formats other than the native bil and tif. I have seen the behavior you mention, but it is inconstant and dependent on how the file was saved into an img format. It ...
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4 votes

Matching colours in already mosaiced single image?

Histogram matching works by forcing the histogram of one image to match as closely as possible the histogram of a second target image. I'm afraid that it won't work on a single image. (There is the ...
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  • 10.8k
4 votes

1m cell size equivalent value in decimal degree

Assuming a spherical Earth of radius, R = 6,371,000 m, and a latitudinal (N-S) arc length, a = 1m, then the latitudinal arc angle, dφ = a / R = 0.000000157 rad = 0.0000089932 deg, but note what ...
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  • 8,594
4 votes
Accepted

Remove clumps of pixels in R

#reproducible example r <- raster(ncols=12, nrows=12) set.seed(0) r[] <- round(runif(ncell(r))*0.7 ) rc <- clump(r) #extract IDs of clumps according to some criteria clump9 = data.frame(...
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  • 9,789
4 votes

Using Erdas for land cover land use change detection

ATCOR for Erdas Imagine will convert DN to true reflectance--this step is critical for change detection analyses. Then you can use DeltaCue add-on in Erdas Imagine to detect land cover change. More ...
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  • 50.2k
4 votes
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Is possible to merge landsat 8 with High Resolution Satellite Imagery?

It is technically possible to use the pansharpening algorithm with different sensors, and all your tagged software have pansharpening tools (sometime . However, the quality of the outputs will depend: ...
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  • 48.5k
4 votes
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Existence of fiducials marks in a digital camera file

fiducial mark are used to define the coordinate system of the photograph. With film photograph, the paper moves under the objective and can get further distorted during storage and development, so you ...
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  • 48.5k
3 votes
Accepted

Creating a Time series NDVI map

As you are trying to compare these images, the key is to do everything to make the images to be as comparable as they can be, so the actual changes can be seen. Here are my steps: Acquire Satellite ...
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  • 618
3 votes

Using sieve filter in ERDAS Imagine and/or ArcGIS for Desktop?

Using Erdas, the Sieve tool is located: Raster tab > Thematic (Raster GIS group) > Sieve Also, a widely accepted approach is to use GDAL's gdal_sieve.py, describes as follows: The ...
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  • 50.2k
3 votes

How to rescale data ranges in ERDAS?

Rescaling an NDVI or EVI from -1 to 1, to 0 to 1, uses the Rescale function (under Raster, Radiometric). Clipping the top and bottom 0.5% is a percentage linear contrast stretch. To do this in ERDAS ...
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  • 8,906
3 votes

Floating point to 8-bit unsigned raster conversion using ArcGIS for Desktop or ERDAS IMAGINE?

You will want to stretch your floating point data from (-1 to 1) to (0 - 255). You can accomplish this very easily in Erdas Imagine: Raster tab > Resolution Group > Radiometric > Rescale
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  • 50.2k
3 votes
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Stereo Analyst & ArcGIS 10.1 - volume calculation

To calculate a volume, you need the 3D Analyst extension. 3D Analyst has several ways to calculate volumes. All methods require the data to be in a projected coordinate system. You can use TIN or ...
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  • 1,351
3 votes

Shifting cloud mask in Erdas/ArcMap/Py Script

There is a simple way you could do this using a python script, however it does not truly create a cloud shadow. For more information on creating a cloud shadow see this paper by Zhu and Woodcock (2014)...
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3 votes

Shapefile Conversion to ERDAS Signature editor

You can use the Signature Editor in ERDAS to use Shapefiles to create signature files. The Signature Editor is found under the supervised classification in the raster ribbon of ERDAS. You must have ...
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  • 698
3 votes
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Deriving slope angle value from DEM using ERDAS Imagine

Have you though of just using the free GDAL tool? http://www.gdal.org/gdaldem.html It can run in windows using OSGEO4W and can ouput .img files. For Imagine 8 it goes something like... From ...
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3 votes

Pro vs Con on using export to JPEG or JP2000 files for large imagery files

JPEG2000 Pros: Better compression than JPEG Supports both lossy and lossless compression, JPEG is lossy only Supports any number of bands, JPEG only supports 3 bands Supports more datatypes (...
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  • 51.7k
3 votes
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How to remove band from stack in ERDAS 2013?

Use the Layer Stack tool in reverse by using your 11 band stack as the input and selecting only the bands you want in the output. For example, in the attached screenshot I added bands 1, 2, 3 to the ...
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  • 50.2k
3 votes

What exactly does hill shade or Shaded relief , if performed on SRTM DEM will output?

Hillshade computes the local illumination from a light source located at infinity (like the sun). Basically, it yields the cosinus of the normal to the face of the terrain and the light ray. This can ...
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  • 48.5k
3 votes

Calculating NDWI in Erdas IMAGINE 2014

the original (GAO 1996) NDWI is based reflectance for the wavelength of 0.86 (NIR) and 1.24 µm (SWIR). This corresponds to bands 2 and 5 if you use MODIS. The equation for MODIS is thus (b2-b5)/(b2+b5)...
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  • 48.5k
3 votes

what is the basic programming language or code language for raster swipe tool?

In OpenLayers Swipe Control is easy enough to use, the following code should set you up: var map; var swipe; function init() { map = new OpenLayers.Map({ div : "map", ...
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