Questions tagged [ndvi]

Normalized Difference Vegetation Index is used to quickly identify vegetation and its condition in remotely-sensed data.

Filter by
Sorted by
Tagged with
2
votes
1answer
14 views

Merging two ImageCollections to create a new index

I am currently trying to calculate the rain use efficiency index for the years 2000-2015 with a Landsat dataset (NDVI) and a CHIRPS (precipitation) dataset. I already have two image collections ...
2
votes
1answer
39 views

Creating NDVI from raster using ArcPy

I have to create NDVI's for multiple raster images, and so want to find out the most efficient way to do it. The code below works, but I wondered if there was a more efficient way to do it? # ...
1
vote
1answer
39 views

Reclassify NDVI and count number of pixels above certain threshold in Google Earth Engine

Following on from a previous question (NDVI reclassify with mean +1SD as threshold in Google Earth Engine) I have managed to show the pixels that have value higher than NDVI mean+1SD at the estuary ...
1
vote
1answer
31 views
+50

range map: Layer error: Number.divide: Parameter 'left' is required. error when print the dictionary

I have code that calculates NDVI, then calculate statistics inside a dictionary and then based on statistics calculte 3 layers that later on mosaiced. The problem is that for some reason I get this ...
1
vote
1answer
38 views

Calculating NDVI using Rasterio, Python

Below is my code for calculating NDVI using Landsat 8. I have used band 4 and 5, but I am not getting any output. How should I get the output image? import numpy as np import rasterio import ...
0
votes
0answers
18 views

Batch downloading LANDSAT imagery based on nearest image capture date

I have a 30-year large dataset (100,000+ points) of insect outbreaks (0=no out break, 1= outbreak) throughout Australia. I am interested in seeing if the spatial configuration of vegetation is a ...
0
votes
1answer
44 views

NDVI reclassify with mean +1SD as threshold in Google Earth Engine

I'm trying to do ndvi reclassify in google earth engine. I know exactly how to do it in Arcgis but I'm very new with GEE and I got stuck with javascript. What I want to do is to use mean + standard ...
0
votes
1answer
31 views

Collection.toList: The value of 'count' must be positive. Got: 0

I have a code that suppose to count number of pixels in a polygon and to add it to the polygon as a dictionary. First NDVI calculted and then differrent ranges inside the polygon should be calculte: ...
0
votes
0answers
22 views

Iteration between different polygons in one layer

I am trying to create a code that will calculte the mean NDVI value for each polygon,the standard deviation , then std/2 and then will classify the pixels inside each polygon according to the next ...
0
votes
0answers
33 views

Min NDVI estimation from NDVI time series

I'm trying to estimate max min NDVI values from the NDVI datasets that came from Landsat images 4-5-7-8. For the max NDVI I used the "qualityMosaic" and it seems that it works okay, but for the min ...
2
votes
1answer
53 views

Different min and max NDVI values with different approaches using Google Earth Engine

I'm trying to calculate the vegetation fraction for land surface temperature calculations of a single Landsat 8 image. I need to find the min and max NDVI of the scene. I've masked the image and ...
0
votes
0answers
17 views

Are there annual or monthly NDVI high res datasets? [duplicate]

I'm looking for a source of high res (250 meter seems the highest res available for MODIS?) NDVI composite datasets for either an entire year (or monthly snapshots) if not, in a format I can import as ...
0
votes
1answer
38 views

Create Layer of pixels with value higher than 0.3

I have code that suppose to calculte NDVI and calssify it according to the NDVI value. I have tried to add a function that will create for me a new layer that will have only pixels with value higher ...
0
votes
0answers
13 views

Export results of MPRI and NDVI to CSV file? [duplicate]

How can I export the result of MPRI or NDVI (which are rasters) to a CSV file? I want to interpret and compare MRPI and NDVI.
1
vote
0answers
18 views

Why is ReduceRegions returning null values when I reduce using a feature collection?

I am running a landtrendr script which returns some disturbance-related values (year of disturbance, duration... among others) for an area. I would like to reduce the result of the area by a large ...
0
votes
2answers
43 views

Reclass NDVI value using a function

I'm trying to reclass the values of a sentinel 2 NDVI creating a function but I don't know exactly how do to it. What I exactly want is: When NDVI values are between -1 and 0, return (-1) ; 0 and 0....
1
vote
0answers
18 views

Looping workflow across attribute table using Google Earth Engine

I have a shapefile asset loaded with an attribute column called "OBJECTID". I would like to run the following script for every ID number in the attribute table, and produce an output table. /// ...
0
votes
1answer
37 views

Update image visualization parameters from slider UI elements in Earth Engine

I'm trying to change the visualization parameters (min and max) of NDVI images in an Earth Engine App with slider controls. The result is an animation of styled images. The animation part works well, ...
1
vote
1answer
27 views

Losing pixels values when counting by value

I have a script that calculates number of pixels with NDVI values that are higher than 0.3, 0.5 and 0.7. My code runs with no errors, but it get value 0 and doesn't really count. what can be the ...
-1
votes
1answer
37 views

Export fitted values from time series regression in Google Earth Engine

I have used harmonic regression to model NDVI values in GEE. Now I would like to export fitted values for every half-month timestep. Unfortunately, much of the exported cells rasters have 'nodata', ...
0
votes
0answers
47 views

Export fitted values image of harmonic regression NDVI in GEE

I am trying to export rasters of harmonically-regressed fitted values of NDVI for every semi-monthly timestep (twice a month) for a given year. When I visualize the image (mosaic) created using the ...
-1
votes
1answer
37 views

Add an NDVI band to NAIP imagery and then chart it (using Google Earth Engine)

I am attempting to calculate NDVI from NAIP imagery, add the NDVI band as an additional band to the NAIP imagery and then chart it. I am easily able to calculate NDVI from NAIP imagery with the below ...
2
votes
1answer
41 views

Obtaining NDVI data only for imagery within an imported polygon

I am trying to visualize NDVI for a specific boundary that I have imported from ArcMap. When I filter the NAIP imagery by the boundary it works perfectly, but when I try and filter the MODIS by the ...
1
vote
1answer
39 views

Extracting NDVI by regions defined by certain column using Google Earth Engine

I am trying to extract NDVI values by regions of a certain polygon shapefile. I need, as output a graph (or a table) where the regions are defined by a certain column, called 'FID_incend'. I need ...
0
votes
1answer
85 views

Creating NDVI time series from single polygon of shapefile using Google Earth Engine

I am new in Google Earth Engine, I am trying to plot ndvi timeseries from a single polygon of shapefile, but when I run the code I get "Error generating chart: Collection query aborted after ...
0
votes
0answers
48 views

MODIS DAAC2Disk fails with “Unable to obtain ECHO token”

I have been using the tool DAAC2Disk to easily download NDVI using an extent. However recently the tool fails with the error: "Unable to obtain ECHO token" Has anyone encountered such error? Or know ...
0
votes
3answers
76 views

Different NDVI in Python vs QGIS

When deriving NDVI out of a Sentinel-2 image - S2A_MSIL2A_20190502T074621_N0211_R135_T38SLF_20190502T102541 - I am getting a strange result when doing it in python vs in QGIS. In QGIS (using raster ...
1
vote
2answers
53 views

gdal_calc equation results in error: divide by zero

iIt is quite obvious to me that the rasterset A, B within the NDVI equation, --calc='"((A-B)/(A+B))"' with cell_value=0 will lead to the above error (division by zero). How can I avoid the error?
0
votes
1answer
60 views

Irrigated Area Recognition in Google Earth Engine

I'm using Google Earth Engine with the Python API. I have calculated the NDVI value over an area, set a threshold and the result is a layer where black areas exceed my NDVI threshold (don't pay ...
2
votes
1answer
43 views

NDVI chart of sampled points

I'm working with Sentinel 2 satellite and I have sampled on the map 4 blue points indicating an irrigated areas, and other 4 red points for non-irrigated ones. Then, I have considered 4 collections, ...
1
vote
0answers
34 views

Calculate the annual mean NDVI for a region using the Maximum Value Composite

I first used the Maximum Value Composite to generate a annual NDVI for a watershed, and then calculated the mena NDVI for the entire basin. I don't know if this code is correct. In addition, I want ...
-2
votes
1answer
69 views

Google Earth Engine: Use multiple bounding boxes to extract mean VI value

I am new to GEE with no prior Javascript knowledge. I am trying to find a way to use multiple bounding boxes (which are in bottom-left point x,y and top-right point x,y) from a csv file in order to ...
1
vote
0answers
59 views

Chart - trendlines - slope - NDVI - visibleInLegend: true - GEE

I am using the following code in GEE to calculate the trend line: ndviChart.setOptions({ title: 'NDVI (Sentinel 2)', vAxis: {title: 'NDVI'}, trendlines: {type: 'exponential', 0: {color: '...
1
vote
1answer
77 views

Arcpy reclassify with function

I have two rasters, one with NDVI values, and one with greyscale values (=(red band + green band + blue band) / 3). The rasters have the same name. I need to reclassify them in arcpy with the ...
0
votes
1answer
56 views

Reduce.region odd result in GEE, however the map seems to be correct

I'm using Google Earth Engine to calculate the 5th and 95th percentiles of the intraannual coefficient of variation (CV) of the NDVI within a polygon (my area of interest). My code actually runs and ...
1
vote
1answer
37 views

My NDVI values are way out of range - GEE

I am supposed to collect NDVI values for some states in the USA. I understand NDVI is supposed to be between -1 and 1, but my values are in the 1000s. Can someone please help me with the ...
1
vote
0answers
47 views

Comparing NDWI regions with a given shapefile Google Earth Engine Python?

With the code below, I computed the NDVI, NDWI and NDWIMOD indices of a R.O.I. in order to detect water areas in that R.O.I. Now, my goal concerns to compare the water areas with a given shapefile ...
1
vote
0answers
21 views

Problem merging/clipping MODIS rasters in QGIS

Im pretty new to QGIS and am having some trouble making a NDVI map for Mali. To cover the whole country I need 5 MODIS NDVI tiles, however every time I try to merge them I get a "the following layers ...
0
votes
0answers
26 views

Google Engine: Time Series Analysis with multiple point data [duplicate]

I have multiple points representing different crops for an area (say 100 per crop, and 5 types of crops). I compute the Sentinel2 NDVI for a period of one year. Even if I filter for just one type of ...
0
votes
1answer
153 views

Export stacked layers of images as a thumbnail URL in GEE

I am computing different normalized index like NDVI, NDWI, NDBI, UI and adding them as layers stacked on top of Sentinel 2-1C Image patch. I would like to download the generated stacked image as a ...
1
vote
1answer
101 views

Using NDVI along with regular RGB and NIR bands for image classification

Is it plausible to use NDVI along with other regular bands for image classification related data processing? Recently, I came across a comment that RED and NIR band might interfere with NDVI or vice ...
1
vote
1answer
43 views

ArcPy: Create NDVI with Raster Calculation and Map Algebra

My target is to create NDVI Rasters but I'm stuck with python loops, since I'm new to that, so sorry for a maybe basic question. I have 2 folders, one with rasters (tif) with the red band, the other ...
0
votes
1answer
51 views

Duplicate NDVI measurements on Graphs in Google Earth Engine

I have created the following code below for graphing the NDVI at areas of interest and printing it to the user interface. The problem I am having is that on the same date there are two different NDVI ...
1
vote
0answers
21 views

I am trying to create an NDVI image using an RSGISLib python script, but it is displaying no data values

My script runs fine and creates an output, but the output is displaying values all the way down to -999, rather than just having the values present in the NDVI result (0-1). I can create an NDVI image ...
1
vote
1answer
25 views

Image analysis about area

I tried to find out the lake's area in an image raster - I used NDVI and reclassify then I got a whole value file like this. Is there anyone can tell me how to divide them to each polygon? Or I can ...
1
vote
0answers
31 views

Scaling factor for MODIS (MY09GA 006 or MYDTBGA 006) product for timeseries data

I was using Modis data (MYDO9GA) product for my research and I was following this document as a user guide. https://landweb.modaps.eosdis.nasa.gov/QA_WWW/forPage/user_guide/MOD09_UserGuide_v1.4.pdf ...
2
votes
0answers
64 views

Calculating NDVI values for specific zones using zonal statistics using QGIS

I am currently working with multispectral data from a MicaSense RedEdge M on a plot size study in wheat research plots. I want to conduct zonal statistics to calculate NDVI for individual plots. I ...
0
votes
1answer
25 views

Reading value and coordinates of every pixel post NDVI calculation in ArcGIS Desktop?

I have a pre forest fire image and a post forest fire image. I would like to make a comparison between the coordinates and the values of both images pixel by pixel. How would I access the value and ...
0
votes
0answers
18 views

Rescaling NDVI from 0-255 to -1-1 in ArcGIS Pro?

My NDVI raster ranges from 0-255. My goal is to get values from -1 to 1. If using the Raster Calculator, what would be the correct equation to achieve this? I'm working in ArcGIS Pro.
1
vote
1answer
156 views

Calculating statistics for multipolygon in Google Earth Engine?

I have a shapefile which contains many crop plots, around 2000. I need to calculate NDVI (normalized difference vegetation index) and then calculate statistics for each one of the 2000 plots ...