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12

Panchromatic images are created when the imaging sensor is sensitive to a wide range of wavelengths of light, typically spanning a large part of the visible part of the spectrum. Here is the thing, all imaging sensors need a certain minimum amount of light energy before they can detect a difference in brightness. If the sensor is only sensitive (or is only ...


12

You can get Sentinel-1 data from scihub.esa. Requires only registration (And most likely, non-commercial use). As Sentinel-1 has just become operational the archive is not very extensive but should grow quite quickly. You can set request data-access propospal on Alaska Satellite Facility. Some data open access. For ALOS-PALSAR you must be a resident of the ...


11

Have you looked at using FWTools? There is a python script called gdal_merge that is available within FWTools. You can use a list as input. The command with usage would be: gdal_merge -o c:\temp\output_image.tif -q -v --optfile c:\temp\rasterlist.txt


8

GDAL supports .img format, both the basic Imagine and the extended Imagine (greater than 2GB), thus any software that utilizes GDAL drivers would support ERDAS Imagine. The most workable and well documented that I have seen is QGIS. It is also open source and therefore free.


7

Posterizing was a great start: it eliminated most of the compression artifacts and simplified the cartography enough to enable additional cleaning. Much of the cleaning of a categorical raster involves so-called "morphological" operations. These include expanding one category into its neighbors, shrinking it back again, and region grouping contiguous ...


6

If you open up the Properties dialog for the picture element, you can state that you want it to be saved with the MXD:


6

If you're using Python I'd recommend using the GDAL library, which has it's own Python bindings. Assuming you've got both GDAl (see this GIS StackExchange question for details on how to install on windows) and numpy installed, your code could look something like: from osgeo import gdal import numpy as np #Open our original data as read only dataset = ...


6

If you want to show your geometries as vectors instead of images there are a couple of tricks that you can apply to reduce the load of your page: Use TopoJSON instead of GeoJSON Remove all the attributes that you are not going to use in the applicaation and also the whitspaces. Taking into account your visualization scale, simplify your geometries and ...


6

Only managed to find a couple of sources for SAR images and data: You can download SAR images from here which are mostly focused on ecological sites such as forests: You can download SAR samples from here which contain fairly large datasets (note: the last 4 links at the bottom of the SAR section are dead) Hope this helps.


6

Your understanding is correct. Obviously, you aren't limited to just two points in time, but that is only a minor variation. Multi temporal information is generally used for change detection, but it also provides a good tool to take phenological information into account when doing vegetation classification.


5

Under'Options', choose the 'CRS' tab, and see the choices for new layers. Choose either "Use project CRS", or 'Use default CRS displayed below'.


5

you can either check "update georeferencing" or create a new rectified image using "rectify". These tools are in the drop down menu of th georeferencing toolbar.


5

Yes, there is a way to do that. In the symbology palette for the overlay raster, you can select the Display Background Value (R, G, B) _ _ _ as ___ option (see screenshot for a raster I have doing the same thing with a white background. Assuming your background image is truly all white, your values will also be 255, 255, 255 in the boxes. Make sure to select ...


5

I hacked together a solution for this and wrote a blog article a while back on a very similar topic, which I will summarize here. The script is intended to extract a river from a 4-band NAIP image using an image segmentation and classification approach. Convert image to a numpy array Perform a quick shift segmentation (Image 2) Convert segments to raster ...


5

This is a known issue with ESRI. Their Page suggests these following workarounds (quoted from ESRI): Use one of the following two solutions to solve this issue. It is highly recommended to download and use ArcGIS Pro to perform all printing and exporting functions. ArcGIS Pro is not limited by the graphical device interface (GDI) ...


4

Though I am not able to understand the difference between the standard deviation output and the percentage output and what is the significance of using one over the other? Those refer to the threshold used to decide whether there has been any change between two images. For percentage change, it uses a symmetric relative difference formula to ...


4

From the USGS FAQ: the blue band is useful for "Bathymetric mapping, distinguishing soil from vegetation and deciduous from coniferous vegetation". It's my experience that you get better results by using band combination, however.


4

GIS file formats contain georeferencing information. This ties image pixel coordinates to grid references in a projection system, in this case British National Grid. There are lots of ways this information can be stored depending on image format. A basic tool to get you started is gdalinfo which will query the extents of the image in British National ...


4

Of course you can change the OpenLayers default z-index. Just overwrite the z-index default range before anything. OpenLayers.Map.prototype.Z_INDEX_BASE.Feature = 2000; OpenLayers.Map.prototype.Z_INDEX_BASE.Popup = 4000; OpenLayers.Map.prototype.Z_INDEX_BASE.Control = 5000; var map = new OpenLayers.Map(); ...


4

Achieved it by adding a pictureMarker of protractor PNG image. protactorLayer = new esri.layers.GraphicsLayer(); map.addLayer(this.protractorLayer); protractorGraphic = protactorLayer.add(new esri.Graphic(geometry, new esri.symbol.PictureMarkerSymbol('images/protractor.png', 250, 250)));


4

Try converting your file to another/the same format (Raster/conversion/translate(convert format).There you can define a value for "no data", which you can set to a number different than 0. Hope it helps


4

JAXA have made global L-band SAR mosaics at 25 m spatial resolution available from the PALSAR sensor: http://www.eorc.jaxa.jp/ALOS/en/palsar_fnf/fnf_index.htm Registration is required to download the data.


4

It looks like GDAL is describing the outer edge of the 'origin pixel' and Arcmap is refering to the center of the origin pixel. If you add half the resolution of a pixel they'll match fine. This definition is often different with different software, it doesnt really matter, though you should know what you're looking at so you can take it into account. One ...


4

It's normal that azimuth and range resolution of SAR sensors differ, because they depend on different variables: The azimuth resolution (AR) of a SAR system is: AR=Length_of_antenna/2 The slant range resolution (SRR) of a SAR system is: SRR=(Speed_of_light*pulse_length)/2 The ground range resolution (GRR) of a SAR system is: ...


4

Otsu's method does not really care about actual values since it tries to minimize the total variance within classes while maximizing the distance between the classes. So, you could just run Otsu on your original data (no need to rescale) and it will provide you with the optimal threshold to use to achieve the goal listed above. I don't know what is your ...


3

Combined pan-sharpening, contrast stretching, and gamma stretching functions If you have access to ArcGIS (and the Spatial Analyst Extension) you can use the technique described in this blog to "blend" DEM (or imagery) with shaded relief. The main disadvantage of this solution is that it is static; you need to produce an RGB raster from your DEM so if you ...


3

In theory, it should be possible to create one layer, add images as features with externalGraphic, and set their size (graphicWidth, graphicHeight) dynamically by context function. This will "emulate" georeferenced images. In practice, first problem is - after changing zoom, when feature's origin is not on screen, it's not displayed. Zoom in in example, and ...


3

I would use style's context object which calculates graphicWidth and graphicHeight depending on current map resolution. It applies to you first option (Vector layer).


3

You have tagged your question with OpenStreetMap, so I am assuming you are interested in the data in OSM's zoom levels. Please have a look at: Zoom Levels Usually you would not look at the whole world, at the same zoom level, as you would a small city. Your example is at zoom level 17, which has a scale of 1:4000. You would look at the world either at ...


3

Another approach that doesn't generate a new image - specially in a situation where you have a plethora of large raster datasets - but uses the existing ones could be using the gdalbuildvrt command line: it gives you more control for the output through its options and you don't need to provide the txt file with the raster list if all of your images are in a ...



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