Questions tagged [sample]

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Extract values from a raster (imported as a NetCDF file) to table - problematic date/time column

I have a NetCDF file with sea surface height data, which I imported into ArcMap as a raster. I plotted the points and extracted the values at each location using the sample tool. In the raster, each ...
D. Kyriakoudi's user avatar
3 votes
1 answer
95 views

QGIS sample raster via field calculator

I'm trying to sample a raster by a point feature layer. I don't want to use the QGIS sample raster tool, since it creates a new layer/file everytime, which adds additional steps and unnecessary ...
Honeybear's user avatar
  • 2,386
0 votes
1 answer
58 views

gee ranadomPoints fails:Polygon too large to be randomly sampled. Must be smaller than a hemisphere when image is not so huge

I want to sample random points over an image I access using geemap. I was trying to do it as following: #access elevation image and clip it with the feature collection img = ee.Image('USGS/SRTMGL1_003'...
ReutKeller's user avatar
  • 2,107
1 vote
1 answer
337 views

Sample points randomly on an image using Google Earth Engine

I have an image ('biome') and a feature collection ('grid'). I want to sample points on the image, precisely 10 points per feature(a grid cell). Also, I want to drop points that intersect the masked ...
yoyo's user avatar
  • 21
1 vote
1 answer
311 views

Sample points from each feature in a featurecollection (Google Earth Engine)

I created a grid (featurecollection containing various rectangular features) by coveringGrid function, and now I want to sample 10 points within a feature, and for every feature in this ...
yoyo's user avatar
  • 21
0 votes
0 answers
108 views

Creating sample points that cover all values of underlaying raster using R

I need to create sample points to extract the values of a predicted raster. The values correspond to the predicted classes and are NOT occurring in the same number. In order to be able to create a ...
talocodat's user avatar
2 votes
1 answer
69 views

Randomly sample points within polygons

I am working in QGIS 3.24.0. I have 200 vector layers in the form of circular buffers (same size, different extent) and a single layer of points (n=1,000 or so) contained within those buffers. 2 of ...
jmf's user avatar
  • 29
1 vote
1 answer
103 views

Created weighted sample points in ArcGIS Pro

I have a classified satellite image and I want to create a confusion matrix to check its accuracy. Instead of doing a "simple random sample", I want to do a weighted sample, where there is a ...
TBI_PRK's user avatar
  • 11
5 votes
0 answers
160 views

Select subset that is spatially equally distributed

Let's say I have a table point with ~10.000 rows. Each row contains a POINT(x, y). I also have a table polygon with POLYGONS(...). The points in the point table are unequally distributed in space. ...
four-eyes's user avatar
  • 3,368
0 votes
1 answer
137 views

How to find if a non-random subsample of a raster is significantly different from the raster using ArcGIS 10.7

I am attempting to find a way to test if the values from a non-random sample of my raster values is significantly different from the raster values as a whole. In this case, I have extracted values for ...
YamCham's user avatar
  • 113
0 votes
1 answer
52 views

Tracing back single class sample sizes of a random forest classification model (.pkl-file) [QGIS 3.16 - EnMAP Box - RFC]

A couple of weeks ago, I created some prediction models with the EnMAP Box Classification Workflow. In some of the models I reduced the sample size for some classes as shown in the image below. Here, ...
jaysigg's user avatar
  • 497
2 votes
2 answers
612 views

Randomly sampling polygons from polygon grid using the spatialEco package in R

I have a polygon grid (epsg:24381) from which I want to randomly select some polygons. Whenever I try to perform the sampling I'm getting the following error: Error in h(simpleError(msg, call)): ...
Nikos's user avatar
  • 968
1 vote
0 answers
35 views

Appending ID column back into sampled image

With a lot of help I recently figured out how to extract NDVI values for a specific date for a collection of GPS points (Extracting NDVI value for GPS points - how can I extract NDVI value for ...
EmmaE's user avatar
  • 23
1 vote
1 answer
267 views

Google Earth Engine: Sampling through image collection [closed]

I am trying to get samples from each image in an image collection and merge them into a single feature collection. So, I wrote the following code (https://code.earthengine.google.com/...
David Carchipulla's user avatar
1 vote
0 answers
311 views

eCognition export samples as a shapefile problem

I need sample shapefile for the other project but when I try to export it, it gives me an error like domain is empty(no images object available). How can I get the samples as shapefile?
geomatics's user avatar
1 vote
2 answers
281 views

Combining imagery, masking and sampling in Descartes Labs Platform

I am trying to sample data from Descartes Lab imagery to train a random forest classifier in the Descartes Plaform for an agricultural region. I have already written a script to prepare the imagery of ...
Madeline Lisaius's user avatar
-1 votes
1 answer
116 views

Creating random points with "CreateRandomPoints_management()" function of ArcPy, with minimum distance

I've been trying to create random points to sample some locations based, at first, on a field which contains the number of samples I want. But when I tried at first, in almost every feature it was ...
caio.valente14's user avatar
2 votes
0 answers
621 views

Are there any examples or tutorials showing Branch Version editing with ArcGIS Server JavaScript API?

I am trying to implement branch versioning in an application that I'm building using the ArcGIS Server JavaScript API. I found a blog post showing how to edit branch-versioned data in ArcGIS Pro, and ...
Stephen Lead's user avatar
  • 21.1k
3 votes
1 answer
1k views

Adding column in attribute table with values sampled from raster using QGIS

I am working with QGIS. I have a file with many points, and I would like to sample their values from a raster. How can I add a column in the points' attribute table and fill it with the raster ...
Olivier D's user avatar
2 votes
1 answer
2k views

Implementing proportional stratified random sample in R

I've completed a landcover classification on an Landsat Image and would like to start an accuracy assessment. I'd like a stratified random sample that has a sample number that varies based on each ...
jport's user avatar
  • 437
1 vote
1 answer
500 views

Sampling stratified random points using R for accuracy assessment

I want to sample stratified random points using R. I found the sampleStratified function from the R raster package. This functions samples the same amount of points for each class of my ...
Julian Backa's user avatar
1 vote
0 answers
147 views

Error in sampleStratified() r

I am trying to randomly distribute points in a raster (that has 11 unique values). I followed this posting and was able to recreate it, being partially successful. As mentioned about, my raster has ...
tg110's user avatar
  • 810
3 votes
1 answer
295 views

Sampling list of rasters in ArcPy?

I've been trying several times to sample (Sample tool from Spatial Analysis ArcGis 10.5.1) a list of rasters to a location sample (also in raster format .tif). Here's the code I've been using, and ...
Victoria Lynn's user avatar
0 votes
0 answers
335 views

Randomly Sample Raster Pixels With a Minimum Distance in QGIS

Is there a way I can sample random raster pixels from a satellite image with QGIS or QGIS plugin? I also need each randomly-chosen pixel to have a pre-defined minimum distance from the other raster ...
J. A.'s user avatar
  • 125
2 votes
1 answer
2k views

How can ee.Image.stratifiedSample() be used in Google Earth Engine to select training samples for a binary classifier?

This is a follow-on question to How can one create a binary image from a FeatureCollection in Google Earth Engine? The corresponding minimal example can be found here: https://code.earthengine.google....
Michael's user avatar
  • 1,186
1 vote
0 answers
778 views

R raster - take stratified sample

This question was posted in stackexchange, where there were no views/comments/answers. I have a raster file and would like to take a stratified sample. library(raster) f = system.file("...
Henk's user avatar
  • 165
1 vote
0 answers
48 views

Kriging with a non-uniform (not space filling with concentrated data in certain regions) sampling design?

I am using Kriging for optimization where local searches are often carried out. However, because of these local searches my sample design becomes poor and my Kriging prediction as well as variance ...
optimizationguy's user avatar
1 vote
0 answers
2k views

Converting table asset data type from 'Long' to 'String'

I am attempting to generate 50 random points per land use class through Google Earth Engine. I have performed this operation before on an earlier instance, where the inputs were the following (1) ...
Johanness's user avatar
  • 392
1 vote
0 answers
457 views

Small sample size for geographically weighted regression; limitations

I am studying West Nile Virus risk factors in a specific county using mosquito surveillance data over a ten year study period. The highest resolution of the mosquito data that could be obtained was at ...
Elizabeth Anne's user avatar
0 votes
1 answer
1k views

Distance based random point selection in r?

To avoid clustering in subsequent analysis I try to randomly select points of a SpatialPointsDataFram with a given distance between the points. The remaining part should be devided for test analysis. ...
parallax's user avatar
  • 1,482
0 votes
3 answers
1k views

Random sampling of many millions of Points or raster cells with ArcGIS Desktop?

I need to test the mean of two very big point shapes. One point shape has around 34.000.000 points and the other around 1.000.000. I have to do a random sample in ArcGIS 10.3.1. Unfortunately, I ...
nora's user avatar
  • 131
1 vote
0 answers
175 views

Random Stratified Sample in QGIS and Scale

I need to sample 7 raster layers all 30 m resolution (as some of the remotely sensed products I'm using are Landsat). I have all of my layers ready to go, but I am not sure how I can conduct a ...
Andrew Budsock's user avatar
1 vote
1 answer
84 views

Sample values from a grid by points in RQGIS

I need to sample values from a grid by points. In RSGA, there is a function called "pick.from.saga.grid" to sample raster data set using points. Is there something similar in RQGIS?
Frauke's user avatar
  • 31
6 votes
1 answer
294 views

Why does the ArcGIS Sample tool skip rows and points?

I'm using ArcGIS 10.4 and want to export XYZ values of a raster (type: GRID) to a text file. I'm following the procedure recommended by ESRI support. However, it seems that the Sample Tool in spatial ...
Markus's user avatar
  • 414
2 votes
1 answer
759 views

Generate sample (Gaussian distribution) and store simulations in raster stack in R

I have a raster stack, one of the raster layers is the mean prediction of a property for that pixel, the second layer is the variance of the prediction. I would like to write a function for ...
MercedesRD's user avatar
1 vote
1 answer
235 views

Sample point elevation from a given contour

I need to sample the elevation at number of predefined location given in CSV format (but could convert to shapefile if needed). My input data is a shapefile of contour lines. Is it possible to sample ...
sendho's user avatar
  • 11