Hot answers tagged envi
10
You can't 'remove' clouds from optical imagery, what you see is what you get; they are photographs and there is no optical data recorded from below the clouds in the same way that there is no data underneath building roofs.
If you use remote sensing data of a longer wavelength than light such as microwave, the water particles in the clouds do not absorb the ...
10
I have used OpenCV in the past to train for object detection for geo. Orfeo Toolbox is a good open source choice as Vascobnunes pointed out. For a closed-source version, you can take a look at Feature Analyst (that also has an ArcGIS extension).
At the end, it boils down to training a support vector machine. There are several libraries that you can use for ...
9
The operative word is Resample, the version link is provided, similar links exist for prior versions of Arcmap. Also be aware of resampling issues associated with the resampling method and the nature of the data being assessed.
EDIT
If you want to go the reverse route (ie decrease resolution) see Aggregate
or Resample but be careful to choose your options ...
7
I am afraid satisfying roof detection cannot be achieved with only one single satellite image. You should try to use other sources of information.
The following article describes a method using a DEM + aerial image pairs + cadastral data:
M. Durupt, F. Taillandier. Automatic Building Reconstruction from a Digital Elevation Model and Cadastral Data: An ...
7
ArcGIS 10 Animation
http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#/What_is_an_animation/000900000001000000/
ArcGIS 10 Temporal Data
http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#/A_quick_tour_of_temporal_data_management_and_visualization/005z00000021000000/
You can record either and export to either image (animated gifs) or ...
4
To do this correctly you need to recover the NIR and visible bands (VIS). This is because, by definition, NDVI is the ratio (NIR-VIS):(NIR+VIS).
To analyze the situation, let's use subscripts (1) and (2) to denote the two 16-day values and no subscript for the one-month value. Observe that NIR-VIS = NDVI*(NIR+VIS). Also, because the two time periods have ...
4
I would like to add Block Statistics as another method to alter the resolution of a raster. Depending upon your specific goals, Block Statistics allows fine control of how pixels are assigned based on:
A user defined neighborhood (e.g. rectangle, circle, wedge etc)
The type of statistics calculated within each block (e.g. mean,
majority, variety etc).
...
4
based on my experience, envi ex is good if you don't have much time and need the data "quickly", if you're using good resolution rasters. in low-res rasters, the regular version, imho, is much better, because you have a better control of the procedure.
if you try the various extraction methods with the same raster in envi and envi ex, the results you obtain ...
4
"Starting with GDAL 1.10..."
"I am using the Python bindings with GDAL 1.9.2..."
GDAL 1.10 hasn't been released yet. Beta 1 was released a short while ago or if you're using Windows, you can grab a build of the current trunk (1.10dev) from GISInternals.
If you're stuck with 1.9.2 for a while, here's some code to parse envi headers (envi.py)
Some ...
3
If your imagery is in ESRI GRID format the editing can be done with the ARIS GRID Editor for ArcGIS:
www.aris.nl/grideditor_arcmap
The ARIS GRID Editor adds a toolbar to ArcMap. This toolbar provides a set of tools to change the value of one or more cells. With these tools it is possible to:
draw a free line (pencil)
draw straight lines from one point to ...
3
I don't think there's a really simple way to do this, but one way would be to:
Create a new polygon layer and create polygons over the areas you want to change the values of.
Code the polygons with the desired land cover value.
Convert the shapefile to a raster.
Use the Raster Calculator to substitute the new values.
Con(("POLYRAST" > ...
3
I encountered similar issues as well with polygons. Maybe you have a similar problem.
Error Message by ESRI: "Invalid Topology (Incomplete Void Poly)"
Actual Error: "Invalid Geometry"
Fix: Run "Repair Geometry" (changes data in-place, be careful, there is no undo)
What happens is that the error reported is not using the ESRI terminology of ...
3
If you want to use ENVI, it's straightforward. You can find out how to do it here
Given that your datasets are univariate (NDVI, temperature, pecipitation), you may want to encode them into an RGB composite dataset and plot a single "map" for each timestep.
3
You could reference individual bands in Arcmap 10 by using the full path name and "\Layer_X" where X is the band you want (Eg: "D:\GIS\layerstacks\1993_stack.img\Layer_27"). So if I wanted to save the 27th band from the stacked images, I would write a simple raster calculator statement like
"D:\GIS\layerstacks\1993_stack.img\Layer_27" * 1
and put it in ...
3
Well from one image only, you can do supervised or unsupervised classification. Try a few times and see if results are good.
Better way, the way I did it, was making orthophotos from images. Then I had footprint of the building so i filtered terrain from the image. Then I did classification of the pixels and created vector objects.
If you have DEMs, or ...
2
In model builder,
iterating rasters from a workspace,
constructing raster file path and file names
feeding the path into Raster Calculator and extend file names with the desired band ID.
defining an output path
This may help.
2
Not using Arc or ENVI, but another option is GDAL. You could also use gdal_translate with the -b option. The command would look something like:
gdal_translate -b 1 input.tif output.tif
Where the '1' is the number of the band you want to extract.
The gdal_translate man page has all the other options you may need.
2
In my experience, ENVI EX provides a rather simplistic method for performing feature extraction using object-based image analysis. I investigated using ENVI EX for a project involving image segmentation and classification, and decided that there was not enough configurability for my needs.
Instead, I find the eCognition provides a far more configurable ...
2
You could classifly your NDVI image based on the index pixel values from -1 to 1. Pixels that have a value of less than zero show no reflectance in the NIR band. Values from 0.1-0.2 are usually from soils that reflect in the NIR, and values from 0.3-1 (increasing in vegetation density) are dense vegetation canopy.
Within ArcMap you could use the ...
2
You can achieve this using the numpy.argmax() function. Enter the following into the Python console (adjust to taste):
import arcpy
import numpy
# convert the raster to a 3-dimensional numpy array (x, y, band)
values = arcpy.RasterToNumPyArray("ras2")
# calculate the index of the maximum value along the band axis
#(1-based, rather than the default ...
2
Most MODIS QA data (including the Cloud Mask data) are not stored as separate raster bands, where each band is a grid where each cell is one value of one QA data field. Instead, the QA data are concatenated into strings of bits. So instead of having Band 1 be 00 and Band 2 be 11, they just concatenated them (right-to-left) as 1100 which is a completely ...
2
Have you written IDL .pro programs before? It has a couple of functions such as READU and READ_BINARY. You'll need to know your data type (integer, float, etc.), the interleave (bip, bil, or bsq), and possibly the number of samples, lines, and bands if there's no .hdr associated with your binary dataset. Here's a starting point to get an overview of ...
1
Just in case ArcMap doesn't work, you might want to try GRASS' v.clean tool. You can install GRASS with QGIS. After installing:
Cleaning of topology of a SHAPE file using the GRASS Toolbox
Load the SHAPE file into QGIS
Use existing GRASS mapset (or create a new one) with matching projection settings
Now you have to transfer the SHAPE file ...
1
It appears that the source of the problem lies in the fact that I am only selecting one layer at a time, as you can see in the picture I added, only band 1 is selected.
As a result, the display takes the first line form the first band, and instead of adding the first band from the next 5 bands, it doesn't, then add the 7th line from band 1, then the 13th ...
1
You may have a BIP (Band Interleaved by Pixel) or BSQ (Band Sequential) format. The ESRI help has a reasonable page that illustrates the three interleave methods.
Right-click on the file in the "Available Bands List" window and select "Edit Header..." and switch the interleave from BIL to BIP (if that is what your data actually is, otherwise try BSQ) and ...
1
Assuming this is just a follow on to your previous question about vegetation indices, I would recommend not using the Vegetation Index Calculator. It's quite cumbersome, and (as far as I can tell) more relevant for hyperspectral imagery where you want ENVI to automatically choose the correct band from an image cube based on that wavelengths defined in the ...
1
You could build a mask from your NDVI layer by using the -3000 as your mask value in the Build Mask dialog and then either apply the mask, or just use the resulting binary mask in whatever operation you're doing.
Beware, if you apply the mask and set all those values to 0, and then get your mean, they will still affect your average, like @dmahr is saying.
1
I think you are looking for the MODIS Reprojection Tool - Swath (MRTSwath):
MRTSwath provides the capability to transform MODIS level-2 land products from HDF-EOS swath format to a uniformly gridded image that is geographically referenced according to user-specified projection and resampling parameters. Functionality includes spectral subsetting, spatial ...
1
If you are using MODIS and have the raw data (HDF-EOS), one of the subdatasets documents for each pixel the date of the NDVI/EVI value used in the composite. See http://tbrs.arizona.edu/project/MODIS/MOD13.C5-UsersGuide-HTML-v1.00/sect0005.html#table:Product_MOD13Q1
1
Import image, define projection and export with lower resolution.
Open an empty Project in ArcGis.
a. Click on the following icon:
Define datum.
a. Click with mouse right button at the word “Layers”:
b. Select “Properties”.
c. Go to the field “Select a Coordinate System” and choose as from option list, the desired geographic coordinate system and ...
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