11
votes
Accepted
Transform raster donuts to circles
What you are looking for is a Mathematical Morphology application, Closing to be precise.
If you use GDAL to read your image into a numpy array there is a number of libraries that support this ...
- 9,775
9
votes
EVI and NDVI range value
You are right: the range of the NDVI is limited to values between -1 and 1 due to its' normalization properties.
The negative limit of -1 will be reached if you encounter maximal reflectance (1) in ...
- 176
7
votes
Accepted
Landsat8 DN to TOA Reflectance (minus values)
One flaw in your approach. You don't need to go through DN to radiance.
You can go straight to the DN to reflectance.
Just stick to ((B1*0.00002)-0.1)/0.74457226676389733207607359928648.
- 6,486
7
votes
Accepted
How to extract single band from multi-band radiometry raster using R?
It is not clear on weather you want to subset bands upon reading into R or extract a single band from an existing raster stack. Once illustrated, both are quite simple.
We can use the 3 band R logo ...
- 31.3k
6
votes
Accepted
Rotate ENVI hyperspectral imagery with GDAL
The rotation can be changed from the python API.
The raster grid size, position and rotation parameters can be accessed with the GetGeoTransform() method, and they can be changed with the ...
- 1,502
5
votes
Is LANDSAT 8 Resolution too low for coastline difference measurement?
30m - 45m is a lot of change in a coastline over one year and only very dynamic areas see that kind of change rate. As such, you are correct in your assessment of the impact of imagery resolution on ...
- 6,486
4
votes
Accepted
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:
...
- 49.3k
4
votes
Accepted
Differences in the longitude and latitude between a LiDAR DSM and an optical image
There is nothing wrong with your data. It is just the fact that OS still issues coordinates in OSGB36, while Google uses WGS84:
So you have to assign EPSG:4277 to your degree coordinates, or EPSG:...
- 76.3k
4
votes
Accepted
Writing band names into header (ENVI file type) using GDAL?
You need to use the SetDescription method of the raster band object.
rb = destination.GetRasterBand(1)
rb.SetDescription('band hello world')
rb.WriteArray(myArray)
$ cat /tmp/test.hdr
ENVI
...
- 64k
4
votes
Accepted
Read aviris data with python
You can use numpy's reshape and transpose functions to reconstruct the desired result. And the dimensions of the "desired result" is used in one of two forms which is often up to the user to decide:
...
- 41.6k
4
votes
Explaining ENVI equations?
ge means "greater or equal" (i.e. >=)
gt means "greater than" (i.e. strictly greater, >)
le means "lower or equal" (i.e. <=)
lt means "lower than" (i.e. strictly lower, <)
et is probably ...
- 5,569
3
votes
Accepted
Open LiDAR DEM of the UK with *.asc extension
These are ESRI ASCII grid files:
$ head -6 sd5755_DSM_2m.asc
ncols 500
nrows 500
xllcorner 357000
yllcorner 455000
cellsize 2
NODATA_value -9999
with coordinates in OSGB ...
- 61.5k
3
votes
Open LiDAR DEM of the UK with *.asc extension
GDAL can open this for you, it should be a ASCII file. You can easily translate to tif with
gdal_translate source.asc dest.tif
- 4,212
3
votes
Accepted
Where are the "band names" of an ENVI file once it is imported in R?
I had the troubles myself and couldn't find a solution. To export and import rasters between ENVI and R and keep the band names seems impossible (cf. this related question).
A workaround is to copy ...
- 894
3
votes
ENVI raster file with nodata change to 0
NODATA is a tag, not a value.
If you only need to attach NODATA to a different value you can try:
gdal_edit -a_nodata NEWVALUE input.tif
You strip away NODATA tag (always helpful) with:
...
- 2,159
3
votes
Accepted
Merging georeferenced images that have overlapping information?
If you have ERDAS, this will work Black edge (NoData pixels) in Landsat 8 color correction in ERDAS
For ENVI, you should be able to do that. My currently job I don't have here with me but I have use ...
- 4,141
3
votes
Converting an ENVI raster as point shapefile for editing in ArcGIS?
Using Raster to Point conversion tool in ArcMap is the first thing that comes to mind, it should give you a point in for every raster cell you have (placed in the middle of the cell) and then you can ...
- 3,316
3
votes
Accepted
Classifying different surfaces having almost similar Reflectance responses
The spectral signature that you show on your post are definitely different, therefore you should look at other issues. I would first check that my training samples are correct and adapted to the ...
- 49.3k
3
votes
Accepted
Calculating latitude and longitude values for each pixel corner?
Do I need to some information about the tiff file in order to proceed?
You'll need to know the size of the pixels for a start, and you could use GDAL for that, see:
How do I find out the resolution ...
- 13.2k
3
votes
Accepted
Opening .tab files associated with .lbl files in ENVI
The .tab file can be easily opened in notepad. There you can decide which column information is required for your work and then read this file using python easily.
Then, write the required columns (...
- 454
3
votes
Accepted
Why getting wrong NDVI values resulted from scaled reflectance in ArcMap?
you should either set the calculation in float Float(("nir"-"red"))/("nir"+"red") or multiply by 100 (100*("nir"-"red"))/("nir"+"red"). Your strange results are due to conversion to integer (the ...
- 49.3k
3
votes
Is there a Post-classification Majority Analysis feature on Google Earth Engine (Similar to ENVI)?
Here is an article by the Earth Engine team that does a little explaining on morphological operations within Earth Engine
Fo your case, you may be able to get away with using image.focal_mode() (or ...
- 1,108
3
votes
Digitizing photographs of a map
This is called "georeferencing" and requires knowing the real coordinates (latitude/longitude) of some features on the image.
A Georeferencer program will input your image, then you have a ...
- 61.5k
2
votes
Enhanced Vegetation Index Value
Based on documentation from ENVI software the values should be between -1 and 1, see here
The Enhanced Vegetation Index (EVI) is an algebraic equation of:
EVI = G X ((NIR - RED)/ (NIR + (C1 x RED)-(...
- 3,256
2
votes
Accepted
Parameter names and meaning of their values in an ENVI header file
I believe these are your magic pixel easting, magic pixel northing, x pixel size, y pixel size.
see : http://www.exelisvis.com/docs/ENVIHeaderFiles.html
- 3,862
2
votes
Landsat8 DN to TOA Reflectance (minus values)
Here's a good read on the physics of atmospheric correction, and might help with the issue... I'm a button pushing guy, I feel your pain, at least you can just click that beautiful QUAC or FLAASH ...
- 485
2
votes
NDVI in ENVI: Output format issue
I would need more information to confirm this, but it is possible that you might be saving in an improper numerical format. NDVI is fractional, so if you were saving in at an integer level, all of ...
- 1,333
2
votes
Accepted
Open Sentinel-1 products using ENVI 5.3
You could open, visualize and process SENTINEL-1 image with SNAP (open software from ESA) http://step.esa.int/main/download/. You must have a very good machine.
- 126
2
votes
How to create a map from separate ascii files without merging them?
If your ascii format is one of the GDAL supported ASCII formats you can build a Virtual Raster Catalogue (VRT) from it.
QGIS -> Raster -> Misc -> Build Virtual Raster
QGIS can treat these like any ...
- 9,775
2
votes
Open LiDAR DEM of the UK with *.asc extension
I would go with a two step approach to create a single file from all the downloaded ASCII format files using two GDAL utilities. From within the unzipped file:
Create a 'Virtual Raster' with all the ...
- 887
Only top scored, non community-wiki answers of a minimum length are eligible