Questions tagged [ndvi]

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

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Extraction of NDVI values against each GPS coordinates of Landsat 8 images

My goal is to calculate the NDVI value of each image from 2017 to 2022 but output values show the same value for each image. Kindly look at the code var Date_Start = ee.Date('2017-01-01'); var ...
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If/else statement in Google Earth Engine doesn't give output desired

I am trying to make a correction for the NDVI index calculated from Sentinel-2 using GEE. I found out that for pixels with NDVI meaning in the range (0.5, 0.6) it should be subtracted 0.122..., and ...
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Cloud filtering Landsat collection 2 over specific regions

I'm trying to filter clouds over a specific region for an NDVI time series using Landsat collection 2. I tried filtering with simple cloud score but it doesn't seem to work (maybe because there is no ...
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Calculate transition of different NDVI classes from pre and post NDVI in Google Earth Engine

My competency in GEE is quite low. I have calculated 2 NDVI layers (pre and post-disturbance NDVI). I have separated these NDVI layers into 4 classes according to NDVI values. Now I need to calculate ...
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Trouble creating mosaic raster - image just a grey box

I am having an incredible amount of trouble creating a mosaic raster. I have six .tif raster files that are NDVIs of the same location. I am trying to do some sort of trend analysis on them and I ...
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No features contain non-null values of in graphy

I want to graph the NDVI series by another classified image, but when I graph it there is a wrong No features contain non-null values of "system:index". Howvever I already set the system:...
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Shadows in color infrared images lead to distorted NDVI - Correction?

I have a color-infrared raster and I want to calculate the NDVI. The color-infrared comes as RGB (=NIR,R,G) and 8-bit unsigned data type. I'm using ArcGis 2.9.2 In areas of building and tree shadows, ...
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Is it necessary to convert Digital Numbers to Radiances to calculate NDVI in GEE with Sentinel 2 and Landsat 8 images?

Translated text: I am starting to use the Google Earth Engine platform, and I want to calculate the NDVI for Sentinel 2 and Landsat 8 images. I wonder if I have to do some calculation, first, to ...
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Masking clouds on Landsat8 with Python before NDVI [closed]

I'm new to remote sensing and trying to mask clouds with Python. I'm using the same method in Earth Data Science website (https://www.earthdatascience.org/courses/use-data-open-source-python/...
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"Collection query aborted after accumulating over 5000 elements" Error

I am new to the google earth engine and I am trying to get the NDVI value by running these codes. I enter a Geocode of 380 different points as a shapefile (PLACE) and use Modis... I want to have a ...
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Calculating mean NDVI of two different locations

I am trying to calculate mean NDVI of two location over a chart. I combined the two shapefiles successfully. Then I try to generate time series chart for both locations but only I obtained for one ...
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Downloading time series LST from Landsat

Here is the code I am using to download a time series data representing the LST over a three month period in 2018. However, the code gives me this error A mapped function's arguments cannot be used ...
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1 answer
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Error generating chart: No features contain non-null values of "system:time_start" in generating chart of NDVI

I got this error when trying to produce a time-series chart of NDVI in Sentinel-2. I've already tried something like .copyProperties(image)".set('system:time_start',image.get('system:time_start'))...
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Google Earth Engine - NDVI chart - projection error

Once I multiply NDVI and EVI values with 0.0001, I get an error that is shown below. So I can't get the chart. Error generating chart: Projection error: Unable to compute intersection of geometries ...
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Extracting NDVI for the certain location

I am new to Google Earth Engine and QGIS. I have a Polygon of a city and I have a CSV file for 30000 unique geocode (belonging to the participants who were entered in the study) I want to obtain the ...
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NDVI time series of several areas simultaneously with GEE

I'm not an expert in GEE so I'm relying on pre-compiled scripts that I modify a little at a time. My goal is this: to make a plot in which I compare the time series of agricultural areas and natural ...
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Extracting NDVI value

I am just new to GIS and Python. I have a shapefile of a country and a file with 300 locations (latitude and longitude) from different parts of this country. I extract the NDVI (Landsat 8; band 3 and ...
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Visualization of Time series data of NDVI using GEE

I am trying to perform Time series of my study area, for a period of 6 years, from 2016-2022 (March) using Sentinel-2 COPERNICUS/S2 dataset, in Google Earth Engine JavaScript Web API. This is how my ...
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How do I calculate the maximum value of a pixel across multiple input images in Google Earth Engine to find the maximum NDVI?

I'm doing some NDVi analysis using S2 and because my AOI has quite varied seasons with regards to cropping cycles I need to extract out the max NDVI for each pixel across a number of input images. The ...
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Error in Google Earth Engine: No features contain non-null values of "system:time_start"

Here is my code and I want to find the NDVI in this period of time. However, there is a error that is about system:time_start. function maskS2clouds(image) { var qa = image.select('QA60'); var ...
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Zonal statistics as table on multiple rasters in ArcGIS Pro

I have time series of NDVI for 35 years and I am trying to generate mean and median for five years moving averages(2017, 2020, ...2021) using the zonal statistics as a table tool. I am confused since ...
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1 answer
97 views

GEE NDVI function that removes negative values

Within my NDVI function, I want to either reclassify negative values (-1 to 0) as 0, or change them into 'no data'. Specifically, I want to the do this calculation/reclassification in the code ...
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1 answer
120 views

GEE NDVI time series for multiple polygons each with its own date range

My question extends one asked recently and I am working with the code suggested there as answer: This script takes a set of polygons and for each, averages NDVI over all images within the specific ...
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How to convert several raster files to binary raster using convert-geotiff tool without over writing

I have downloaded 12 raster files (for each month) from sentinel-2 for my study area. And then converted to NDVI(vegetation index). After that I used convert-geotiff (https://github.com/openwfm/...
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Why do I get wrong NDVI, EVI values in crop monitoring?

I have been monitoring agriculture lands with Sentinel-2 S2MSI2A data. I'm calculating NDVI and EVI for the vegetation. The NDVI values are slowly increasing because the growing crops which is look ...
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1 answer
90 views

Google Earth Engine - Get Image with lowest NDVI from a time period

One of the answers to this question (Google Earth Engine - Get Image with highest max Scene NDVI from a time period) provides code which gives a Sentinel image/date with the highest NDVI for each ...
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1 answer
105 views

NDVI mean in polygon between dates, for a set of polygons

I have a set of stations, each has a start and end date for consideration, and polygon of interest. For each station, I need to average the NDVI inside the polygon, and then to average the NDVI for ...
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171 views

GEE code to compute mean annual NDVI time series

I am new to GEE; I am trying to generate a time series NDVI for the July period (peak of summer) between 1984 to 2020. This typically includes harmonizing Landsat 5, 7, and 8. I used the code below ...
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3 votes
1 answer
36 views

Saving orthomosaic .tiff data with symbolization changes using QGIS [duplicate]

I changed the symbolization of my .tiff data such that the NDVI band (Band 1 (Gray)) is represented with 4 colors (RGB derived). Is there a way I can save the .tiff including the symbology changes? ...
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1 answer
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Empty map error for MODIS NDVI time series on Google Earth Engine

I am trying to get a time series of MODIS NDVI for a point, with the script below and it works quite well, except when I try to include the year 2017 where I get the following error message: ID: ...
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Checking if 2 UAV images have similar NDVI [closed]

I have 2 UAV images showing NDVI of the same plant field from different positions (meaning different coordinates, not different capture angle). I am trying to find a solution in order to compare ...
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Error when calculating NDVI using raster calculator in QGIS

I tried to calculate the NDVI with the Raster Calculator in QGIS but got doubled (see image) and distorted results. I have a problem only in QGIS as SAGA works normally. Does anyone know what is ...
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125 views

Creating time series of NDVI data using Landsat 8 imagery

I am trying to calculate the average annual NDVI of Landsat imagery on a forest in Kentucky. The study will occur from 1984-2020. I am writing code specifically for Landsat 8 at the moment, but I plan ...
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1 vote
1 answer
49 views

Creating a Rule in NOAA/CDR/AVHRR/NDVI/V5 to only display NDVI for dense vegetation Google Earth Engine

I'm trying to apply a rule to NOOA NDVI the already classified region to only display dense vegetation areas but it's saying NDVI is not a function. Here is the code: //collecting data using ndvi var ...
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21 views

Enhanced Vegetation Index Value meaning

I calculated the NDVI and EVI for a forest area. I found information to interpret the NDVI values. But I wonder how to interpret the EVI values. I read Huete et. al (2002: 209), the common source. And ...
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3 votes
1 answer
165 views

Calculate and extract layer of NDVI change in Google Earth Engine

My experience and expertise in Google Earth Engine are super low. My study area is Sundarban, Bangladesh. I have 2 NDVI from 2 years (2016 & 2017). I want to find the vegetation change by ...
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1 vote
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85 views

Calculating change area using NDVI in Google Earth Engine JavaScript API

I am new to Google Earth Engine and JavaScript. I am trying to visualize and calculate the changed area from the NDVI of 2 years (Landsat 8 surface reflectance). Can anyone help me to extract the area ...
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1 vote
1 answer
57 views

95th percentile greenest pixel quality mosaic - Sentinel 2 - instead of max

I am trying to combine the approaches suggested in the answers to this post - Google Engine - Make a greenest pixel composite for Sentinel 2 - to make a quality mosaic, based on the 95th percentile ...
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Do I have to do any preprocessing on Landsat 8 Surface Reflectance data sets in Google Earth Engine?

I am working on calculating NDVi and EVI indices from different years (50 year time period) and comparing them. I have a few questions regarding the datasets that I have found on Google Earth Engine (...
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GEE Filter Date for Time ranges

I am not right into GEE. So I want to create a NDVI with comparing 2 timeranges. Actually from 2020-03-01 to 2020-10-01 AND 2021-03-01 to 2021-10-01. So I want to exclude winter season. I am using ...
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1 vote
3 answers
64 views

Is it incorrect to calculate NDVI using DN (Digital Numbers) values instead of using the Surface Reflectance values?

I am working with images from landsat8. I need to know If I can calculate correctly NDVI using digital numbers instead Surface Reflectance values or TOA reflectance equation result
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1 vote
1 answer
37 views

What does "ndvi is not defined" mean?

I'm trying to apply the ndvi function on Google Earth Engine but it shows up the following error: ndvi is not defined This is what I have written: var L5 = ee.ImageCollection("LANDSAT/LT05/C01/...
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How to add STDtime to a collection of processed NDVIs to later create a multidimensional dataset in arc

I have prepared many annual NDVIs in GEE. but at this step to be able to use CCDC Change Analysis in ArcGIS Pro, my NDVIs need to have a dimension named STDtime which literally shows the acquisition ...
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User memory limit exceeded

I calculated median NDVI composite image and later zonal median. While exporting as shapefile, I am getting this error: User memory limit exceeded. Can you help me? Here is my code: // Create image ...
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Rescale NDVI [-1,1] to 0-255 using GEE

I need to rescale the NDVI values [-1, 1] into [0, 255] in order to compute GLCM textures in Google Earth Engine (JS-API). I'm able to compute the NDVI of my imagery using as follows: // load image ...
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1 vote
0 answers
23 views

Characterizing annual NDVI for small site areas with significant time series gaps

I'm looking at 30 years of growing season Landsat 5 NDVI for small areas (three sites, each with 9 pixels). For some years there are only one or two available images due to cloud cover, other years ...
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1 vote
1 answer
58 views

Coordinate points falling off map

I'm trying to extract values from a map figure (NDVIs in this case). My layer with the point coordinates as Lat/Long, added as a CSV file, has the same CRS as the map layer (WGS 84 / UTM zone 36N). ...
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0 answers
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Calculating changes in NDVI in time using Landsat 7 image and Landsat 8 image

I'm trying to understand how much urban vegetation has changed in the past 20 years in my city. The plan is to calculate NDVI for Time1 and NDVI for Time2 and subtract them. BUT Landsat 7 images, that ...
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1 vote
1 answer
80 views

Plot time series for NDVI on Landsat8

I want to select a region on a map and get the time series for NDVI based on Landsat 8 imagery. If possible, it would be better if I can get the image row and path through matching the Landsat tiles ...
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1 answer
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How do obtain a chart of cloud filtered NDVI values from Sentinel 2 imagery in GEE

I am trying to recreate a tutorial from the GEE tutorials (this section) using sentinel 2 instead of landsat 8. I have used some code from another question, which returns almost exactly what I want, ...
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