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Questions tagged [remote-sensing]

Collecting and interpreting information about the environment and the surface of the earth from a distance, primarily by sensing radiation that is naturally emitted or reflected by the earth's surface or from the atmosphere, or by sensing signals transmitted from a device and reflected back to it.

148 questions with no upvoted or accepted answers
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22
votes
0answers
625 views

SNAP vs. GDAL vs. Orfeo - image rescale, histogram cut

I work with a Sentinel-2 .jp2 image (red band, 10950 x 10950 pixels). My aim is to reach the same result what SNAP does with a Python script. See the SNAP method and parameters: So this is my ...
4
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0answers
1k views

Classify image using segmentation analysis using QGIS and OrfeoToolbox

I am working on a project where we have made a RGB orthomosaic using a drone which I want to classify using QGIS. I am not a fan of unsupervised classification, and I started exploring the ...
3
votes
0answers
411 views

Sentinel 2 preprocessing with R

I need to transform Sentinel 2 L1C imagery to preprocessed Level 2A data. Ideally this should happen in R, as the remaining processing stack is already done in R. Are there ready preprocessing ...
3
votes
0answers
128 views

Understanding difference between collocation and coregistration?

I'm a little confused on this topic. I need to put 2 SAR images into same coordinate grid. In ESA SNAP tool, there are 2 options: coregistration: Radar->Coregistration->Coregistration collocation: ...
3
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0answers
250 views

Aligning raster layers in python script

I am wanting to automate the preparation of raster layers from Sentinel-2 to be used in an unsupervised classification. So far, I have been able to write the following script, which will successfully ...
3
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0answers
441 views

Negative reflectance values after topographic corrections (cosine correction and modified Minnaert correction)

I am trying to manually correct the surface reflectance values of some Landsat 7 and 8 images. I'm using Minnaert modified method, which uses the cosine correction as one of its inputs (see below the ...
3
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0answers
287 views

MODIS Imagery Orthorectification (Open Source)

I am looking for an open source free software/tool for orthorectification/Geometric terrain correction of MODIS imagery. I have looked at ESA (European Space Agency) SNAP but this sensor type is not ...
3
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0answers
312 views

Import GPS SINEX (for velocity analysis) into Sarscape or processing with others software

I try to import GPS snx. into Sarscape 5.2 (use GPS Import tool) and getting error 115) ) gps_type : [sinex] 116) ) generate_kml : [OK] 117) ) generate_shape : [OK] 118) ) ...
3
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0answers
87 views

Guide to aerial or space data types and availability

I am overwhelmed by the variety of types of satellite and aerial data (images?) available online. For example, at the USGS Earth Explorer data page, I see AVHRR; CEOS;Ikonos and OrbView; EO-1; GLS; ...
3
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0answers
53 views

Should Endmembers be Normalized for Linear Unmixing?

In biological spectral microscopy, the standard in the field is to use normalized endmembers in linear unmixing algorithms. In most cases, the endmembers are normalized to the maximum value. I have ...
3
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0answers
359 views

Landsat TM, ETM+: what are radiometric calibration coefficient of each sensor to convert DN to radiance

The Landsat TM Image data that comes with zipped folder contains metadata text file in which all necessary information have been written. In order to further process that data, first DN to radiance ...
3
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0answers
305 views

ASTER mineral indices with VINR and SWIR data

I need to run a supervised classification on ASTER data in order to map a rock formation, which is composed of chert. There is no shortage of indices which can be used to highlight silica rich ...
3
votes
0answers
352 views

R: Can raster predict function pass to predict.rfsrc (a prediction function in a parallel verion of RandomForest)?

It seems that raster predict function can pass to predict.randomForest by setting the "type='response'". I am using a parallel version of randomForest package called the "randomForestSRC" and I am ...
3
votes
0answers
431 views

Localized Linear Histogram Match using python

I would like to use the local linear histogram match for filling the missing pixels of a Landsat 7 image with another older image (SLC Gap-Filled Products). Do you have any idea how can I do it by ...
2
votes
2answers
49 views

Can BFAST algorithm be applied to to a whole study area/ ROI?

I am working on identification of breakpoints in Landsat based NDVI time series (1990-2018). I am using The Breaks for Additive Seasonal and Trend (BFAST) algorithm which is a pixel based time series ...
2
votes
1answer
331 views

How to add color-map scale in Google Earth Engine?

I want to add a colormap scale like below in my Earth Engine app. I cannot find a UI component for this. Can I do this in any other way in Earth Engine?
2
votes
1answer
436 views

Extract Pixel Values for Multiple Polygons and Images

I have 21 polygons and for each polygon I want to extract the pixel values inside them for Sentinel 1 images from 2017-01-01 to 2017-06-30. The example below shows how this is done for one polygon. ...
2
votes
0answers
205 views

authentication error for accessing data product on scihub through wget

I am new to Sentinel(overall remote sensing domain) and currently trying to download the data products from Scihub using the wget utility on Windows10 machine. However I am getting the below error. I ...
2
votes
0answers
241 views

NDVI calculation problem

I have photo created by UAV, and I want to calculate bNDVI: (NIR-blue)/(NIR+blue) I have these bands (filter is ok -100%). So using QGIS I have values -0,1-> 0,3 - but bNDVI must be from 0,65->0,...
2
votes
2answers
1k views

ENVI band math incorrect values

I'm attempting to calculate vegetation indices in ENVI 5.2 using level-2 AVIRIS data in band math. The indices I'm working with are Vogelmann Red Edge 2, normalized difference red edge, and red edge ...
2
votes
0answers
140 views

Supervised classification using endmember spectra (using ENVI 5.1)

We are trying to map land cover classes over a small watershed. We have selected training sites (during a field campaign in early 2017) and determined their spectral profiles on a Landsat 8 image ...
2
votes
0answers
26 views

Register an image using mutual information

I want a procedure for registering two images based on their mutual information. I took a pair of georeferenced radar images of the same location, edited the metadata of one so its position was off by ...
2
votes
0answers
49 views

Is there an arXiv-like electronic archive used by the remote sensing community?

Mathematicians, physicists, and (theoretical) computer scientists use arXiv extensively to share their preprints. Indeed, one could say that it's the established way to share one's research. Is there ...
2
votes
0answers
157 views

ENVI shows colors of different RGB code the same in a bitmap image wrongly?

As you see in this picture which I've captured in MATLAB, there are two colors. Red with the RGB code (255,0,0) Brown with the RGB code (138,139,1) I've tried to show the same picture in ENVI, ...
2
votes
0answers
185 views

Image classification: separating pine forest, lowland and upland hardwood

I want to classify 20 feet-resolution 4-band leaf-off image into lowland hardwood, upland hardwood, pine trees, and other (bare ground, water, roads etc). I am thinking to use randomForest package in ...
2
votes
0answers
40 views

eCognition - prevent rounding of raster values?

I have a WorldView2 image, which I would like to segment and classify in eCognition. The image has been pre-processed to Top of the Atmosphere Reflectance, therefore hasvalues between 0-1. The ...
2
votes
0answers
186 views

i.atcorr - Landsat 8

I am trying to apply atmospheric correction to Landsat 8 scenes using i.atcorr. After tons of tests I am still struggling with the correct input and output range. The results deriving from radiance as ...
2
votes
0answers
55 views

Finding pre-processed MODIS products?

I am trying to recognize burnt areas based on some MODIS products and I just realized that I am missing a bunch pixels from the coastline masking. As you can understand that is an issue because I am ...
2
votes
1answer
712 views

Accuracy assessment in Erdas imagine

Is it necessary to do an accuracy assessment for an unsupervised classification done for a Landsat 5 image?
2
votes
0answers
24 views

Image sizes for VHR remote sensing image

I need to compare three or four different segmentation algorithms on very high spatial resolution remote sensing images, with a range between [0.31,1.00] meters/pixel. What image size could you ...
2
votes
0answers
50 views

Issues with using FLAASH on GeoEye data

I am trying to carry out a FLAASH atmospheric correction on radiometricaly corrected GeoEye-1 spatial image (working within ENVI). I am getting the wrong results from my FLAASH correction and believe ...
2
votes
0answers
34 views

Snapping vectors to vertices for ROI delineation?

I am trying to manually extract a set of ROIs in ENVI 5.0. However, I can't seem to successfully line up the vector to be flush with the boundary of the pixels, which means I don't have fine-tune ...
2
votes
0answers
30 views

How to detect undisturbed forest plot in Mudumalai National Park?

I am looking for undisturbed forest plot (without logging for at least 50 years) in Mudumalai National Park (India) or around it. How to detect it using GIS or remote sensing?
2
votes
0answers
99 views

How to determine Visibility Map for Atmospheric Correction

As per Grass wiki: https://grasswiki.osgeo.org/wiki/Atmospheric_correction the atmospheric correction could be done using a visibility raster in conjunction with an elevation raster. With regards to ...
2
votes
0answers
315 views

TIMESAT seasonality data (MODIS EVI)

I am trying to get seasonality parameters from MODIS EVI (MOD13Q1) for Indonesia. I have loaded data from 2013-2015, but the plotted time-series is shifted from what I expect. Indonesia has rice-...
2
votes
0answers
194 views

16-day-MODIS NDVI values seem to be wrong compared to my soil moisture ground data!

I'm using MOD13Q1 product of MODIS for estimation soil moisture. As I know, this product is made up of the maximum value of NDVI of each pixel over 16-day calculated NDVI values. The problem is that ...
2
votes
0answers
411 views

Calculating Aerosol optical thickness from Landsat 7

EDIT I have added question down I am reading one paper and I found method to retrive AOT from landsat 7 image This should be simplifield equation, because they assumed observation zenit as 0. Than ...
2
votes
0answers
100 views

GIS or Remote Sensing technique to map sub-surface features?

I am trying to delineate agriculture tile drainage in Midwest. Does anyone know of any GIS and/or sub-surface remote sensing techniques to detect tiles/objects buried in shallow depth of soil? Does ...
2
votes
0answers
99 views

Important to perform atmospheric correction when attempting to identify coral reefs?

I want to identify coral reefs using multi-temporal Landsat data and Lyzenga's Transformation method. In relation to pre-processing the image, should atmospheric correction be done or not? If not, ...
2
votes
0answers
292 views

What does “Information [18]: Select at least one signature” in the semi automatic classification plugin mean?

I am using the semi automatic classification plug in to classify vegetation and water in a satellite image. I create training shp and signature list. When i hit "classification preview" it gives me ...
2
votes
0answers
83 views

LULC using SAR data

I have a Geocoded SAR data with me. I have to perform LULC classification. I have been given a shapefile (vector data) with the different LULC categories of the region. The region is mainly composed ...
2
votes
0answers
182 views

Landsat Data to Map Slums in India

I am working on a project to answer the following geographic question: How much have slum areas increased in Mumbai, India, since the 1970's (or earliest data). I have downloaded LandSat imagery and ...
2
votes
0answers
72 views

A problem about Correlated-K algorithm of MODTRAN 5

When I use MODTRAN 5.2.2 to run the test case 'CorrelatedK.tp5', I get the following warning information. How I can solve this issue? WARNING: The Correlated-k option was turned off. The ...
2
votes
0answers
62 views

How to create Strips with GCP point distribution for raw GeoEye satellite imagery?

I have raw GeoEye satellite imagery, I just want some guidelines for creating a strip map with GCP distribution. We need to make orthorectification for raw GeoEye satellite imagery, I think it's ...
2
votes
0answers
61 views

“Back calculating” to quantify the “atmospheric effect” of water vapor or other gases in a “corrected” hyperspectral image using QUAC?

I know that when using FLAASH in ENVI, you can produce a water vapor map (caveats considered) from your atmospheric correction. My question is if it is possible to "back-calculate" a water vapor map ...
2
votes
0answers
350 views

Importing GPS coordinates to extract multiple DN values in ERDAS

I have a set of GPS points (stored as a csv for now) and would like to import these points to ERDAS to find the DN values associated with each location. I am able to import a SHP to ERDAS but the ...
2
votes
0answers
2k views

Interpreting NDVI value on water?

There is a surreal thing on my NDVI images. NDVI values on lake is ranging from -0.04 to 0.7. (The lake surrounded by forest and has freshwater). Theoretically, negative value of NDVI is correspond to ...
2
votes
0answers
388 views

ENVISAT ASAR .N1 file is not being opened by ERDAS IMAGINE 2011

I am not able to open ENVISAT ASAR .N1 file in ERDAS IMAGINE 2011. The software has direct read option for files of this format. Whenever I try to open the file, software closes automatically giving ...
2
votes
0answers
2k views

Principal Component Analysis in QGIS

How do I go about to perform a band ratio and Principal Component analysis in QGIS? I need to derive principal components from ratios of landsat TM bands .
1
vote
0answers
6 views

TIMESAT3.3 output errors

When I ran "fit2img" in TIMESAT3.3,I got problematic result image.Contrasted with original image, this result image seemed to be cut into two parts and was badly deformed.I did not know what happened....