Questions tagged [sampling]
Measuring data values at specific, discrete locations.
99
questions
3
votes
1answer
29 views
How to randomly select point within grid (QGiS)
I have a series of occurrence points that I am trying to downsample to 1/20 km to avoid sampling bias. So far, I have made a grid of ~20km squares and have filtered them down to squares with more than ...
1
vote
1answer
97 views
Getting properties of random points in Google Earth Engine
I want to have random points across Peru and their properties (the band values of IMAGE) for statistical analysis in GEE. I found two options which are sampling and random points. I have tried the ...
1
vote
1answer
51 views
How to sample points on specific landcover class using Image.stratifiedSample in Google Earth Engine?
I need to sample NDVI time series on the crop classe defined in the Copernicus GLDAS Landover dataset (value: 40). The logical approach seems to be using Image.stratifiedSample on the landcover, ...
0
votes
0answers
27 views
Generating random points with overlapping polygons in QGIS
The "Random points inside polygons" tool in QGIS works great to generate a fixed number or density of points within polygons; however, because QGIS does not link the polygon ID to the points,...
1
vote
0answers
13 views
What is the minimum sample size when sampling spatialy from existing points [closed]
I have sampled points from an existing shapefile using the Generate Near Table proximity feature to calculate the distance that I later used to select points. Depending on the distance interval I used,...
1
vote
1answer
66 views
Unpack error occuring when sampling raster values to points with rasterio
I'm new to Python. I'm trying to sample raster values to points based on the geometries of a shapefile using the below code but I'm receiving the below error .
import fiona
import rasterio as rio
...
6
votes
0answers
82 views
How does Empirical Bayesian Kriging of ArcGIS Pro handle sampling bias?
In ArcGIS Pro, simple kriging approaches allow you to de-cluster your data before applying a normal-score transformation. According to the Esri guideline, normal-score transformations are only ...
1
vote
1answer
131 views
Is it possible to read a subset of points with the PDAL C++ api?
I am using the PDAL C++ API to read LAS/LAZ data. We're finding some of the tile files are very large (160M+ points), so I wish to take a sample of them. Although the point order in the tiles is ...
0
votes
0answers
23 views
How to get matched pairs from CEM
I am using Coursened Exact Matching to improve balance in my sample. The summary matching results after applying CEM are that 11,128 pixels have been matched:
Sample sizes:
Control Treated
...
0
votes
0answers
16 views
Sample strategy to model continuous variable from conglomerate ground sample units
I´m using data from the Brazilian national forest inventory to model forest canopy metrics with Landsat imagery. The sample units have this conglomerate configuration (picture), which creates a ...
1
vote
1answer
162 views
Extracting different number of points for different class in GEE
I want to write a function that takes class id and number of points for each class as argument and samples points from polygons, returning a FeatureCollection.
I could only write a function that ...
0
votes
0answers
24 views
Google Earth Engine: Collecting Region Samples through image collection and merge them
I am using S1 Imagecollection to start a temporal supervised classification. Firstly, I added polarimetric indexes and other data as bands in each image. Then, I filtered the image collection and got ...
2
votes
1answer
27 views
Generating sampling points - making a series of points in the horizontal centre of a long polygon, equidistant spacing on vertical axis
I have a polygon showing the extent of a beach. I would like to create a series of sampling points along that beach, that are equally spaced north to south (say at increments of 100m to the northing ...
0
votes
1answer
95 views
GEE: Select random sample on known-NDVI-range for supervised classification
I intend to get random samples for training the supervised classification in Google earth engine.
The code here, for example, I calculate NDVI and mask out NDVI < 0.65 (i.e. NDVI >= 0.65 is ...
0
votes
1answer
34 views
Non-random sampling of point vector layer in QGIS
I have a point vector layer with 47.000.000 points representing elevation. It is a regular grid with constant spacing. I aim for rasterization but it is very slow.
I know how to do random sampling but ...
0
votes
1answer
577 views
How to solve “Collection query aborted after accumulating over 5000 elements”?
I am trying to sample image and to get scatter plot of its' two bands- NDVI and db from senttinel 1.
For some reason, probably because of the size of the shapefile, I get the error:
Error ...
2
votes
0answers
93 views
Raster layer stacking and extracting values at points with PyQGIS
I have a dozen single band raster layers in the same CRS overlapping perfectly. I would like to 'stack them one on the other' and extract values at point locations (from a CSV).
After that the ...
0
votes
1answer
508 views
Exporting dataframe - used reduceRegion to sample an image in Google Earth Engine
I am trying to sample the Global Forest Change dataset using randomly drawn points and the reduceRegion function. The way I construct this is:
var sampledPoints = gfc2014_c.reduceRegions({
...
1
vote
0answers
288 views
Stratified sampling in Google Earth Engine
I am trying to get stratified random points out of GHSL (Global Human Settlement Layer) which is a classified raster over my study area (partially Europe and Asia continent), see the picture below.
I ...
1
vote
1answer
52 views
Cut hole in raster with shapefile and sample at closest edges
I have a raster in which I'd like to cut a "hole" with a shapefile. I have points close to the boundary, but inside the hole, and I would like to find the closest point on the edge. To give a concrete ...
1
vote
1answer
56 views
Create point clusters based on grid
I am trying to make a systematic cluster sampling pattern for data collection. The sampling consist of the points placed over the landscape in 6 km span (red). From this major point, I need to create ...
0
votes
2answers
74 views
Random sampling in ArcGIS Desktop
I have 14,033 points representing the location of some weather stations across the 36 states in Nigeria. I want to use an ArcGIS Desktop sampling tool to implement a random selection of 200 points ...
2
votes
1answer
342 views
Creating random plots with coordinates within polygon using R [closed]
I am trying to create random plots in a polygon shapefile and then to plot it with index no as 1,2,3,... along with a legend comprising XY coordinates corresponding to each index no.
Code example:
...
2
votes
1answer
727 views
Extract row & column numbers of a raster at points in QGIS
Is there a tool in QGIS that will extract the row and column numbers of a raster at a set of points? All I have been able to find is the following:
Raster Analysis > Sample raster values
(Plugin) ...
0
votes
1answer
589 views
Export pixel neighborhood in Google Earth Engine [closed]
I have some points and know how to extract the Landsat data at these points and build and export a training dataset to feed an external classifier. But how can I efficiently and automatically build a ...
2
votes
1answer
692 views
Understanding spsample in R?
I have read the documentation for this but still unsure of what the function spsample does.
The documentation is here:
https://www.rdocumentation.org/packages/sp/versions/1.3-1/topics/spsample
I ...
3
votes
0answers
196 views
Creating equidistant sampling points in polygon in QGIS 3.6.0?
I have figured out how to add random points inside polygon boundaries. Although this works well, nevertheless I need a few different things to happen for my application.
What I would like to do is ...
0
votes
1answer
52 views
Sampling land cover map using ArcGIS Desktop?
I have a little bit of a sampling problem in ArcGIS Desktop. I have a classified map with 7 Landcover classes, and this classes are as follows with their percentage: Forest=20.9%, agriculture=6.3%, ...
2
votes
2answers
511 views
Point Sampling Tool pyQGIS
I have several raster files (raster_1, raster_2, [...], raster_n) and a point shapefile. The point shapefile (point.shp) was created using "generatepointspixelcentroidsinsidepolygons" so my points are ...
2
votes
1answer
452 views
How to sample points from temporal layerstacking image including null or masked value in Google Earth Engine?
I'd like to sample points from temporal Sentinel-2 images covering a state, about 13 month's mosaic image were stacked into a new image. When I sampled points on the image, I got nothing. I think ...
0
votes
0answers
860 views
How can I sample points from images mosaic in Google Earth Engine
Rodrigo E. Principe did a great job for Mosaicking a Image Collection by Date (day) in Google Earth Engine (https://code.earthengine.google.com/20ad3c83a17ca27b28640fb922819208)
based the code, I ...
1
vote
1answer
50 views
Automating point feature class placement inside polygons using specific parameters?
I am trying to generate a point feature class of possible plot centers for a research project. The plot centers will be inside of defined forest stand polygons which are aggregated in various ways ...
0
votes
0answers
99 views
QGIS spatial sampling tool for existing points within a polygon ensuring even spread
I would like to spatially sample 10 existing points from within a polygon. I have read the answers from "QGIS point sampling tool really slow for polygons?"; "points within a polygon" as well as "How ...
1
vote
1answer
690 views
Google Earth Engine - how to set masked pixels to 'noData'
Lets say I have a region of mangrove forests (from a classified Landsat image) and I mask out all non mangrove pixels. I view this as a layer on the map and it shows the mangrove forests on the map ...
6
votes
1answer
2k views
What's the difference between sample, sampleRegions, and stratifiedSample in Google Earth Engine?
According to the documentation of GEE,
ee.Image.sample() samples the pixels of an image and returns them as a FeatureCollection, in which each feature has 1 property per band in the input image. You ...
-2
votes
1answer
243 views
Stratified random point sampling in Python
I have a very basic knowledge in Python and arcpy. I want to create a stratified random sampling point on a continuous polygon. So far, I have dissolved the polygon (according to categories) and ...
1
vote
1answer
126 views
ArcGIS Random Point generator producing same points every iteration
I am generating random points to sample within a stratum.
Data Management Tools > Feature Class > Generate Random Points
This works just fine, except that I noticed the points I generated for ...
6
votes
3answers
3k views
Randomly sample from geopandas DataFrame in Python
I am reading a shapefile as geopandas DataFrame and them using pandas subset method to select a region.
geodata = gpd.read_file(bayshp)
geodata.dtypes
geodata.head(10)
OBJECTID FIPSSTCO ...
2
votes
1answer
864 views
QGIS 3.2 - Point Sampling Tool error
I am using "Point Sampling Tool" in QGIS 3.2 to obtain values from a raster file to a point layer.
After selecting the layer with the points, the values to get values from, and defining the Output ...
1
vote
1answer
236 views
How much do leaves on/off affect the number of LiDAR ground returns?
We would like to collect a generic purpose topographic LiDAR dataset over a large region in Belgium. Our minimum requirement is to achieve at least 1 point/m² on the ground. Ideally, we would like to ...
2
votes
1answer
126 views
Sample points based on multiple conditions
Can anyone suggest a QGIS/R approach to sample from a polygon n points that satisfy some conditions depending on underlying raster layers values?
E.g. I have a country polygon and I would like to ...
1
vote
0answers
111 views
Applying mask to Kriging shape in ArcGIS Desktop?
I'm trying to apply an mask to a Kriging image for after apply a Density Sampling Network, but unfortunately I'm not getting good results.
I tried to apply on mask on Density Sampling Network and is ...
1
vote
1answer
922 views
Create random sampling point in each grid's cell
I would like to know how to create an X number of random points in each grid cell.
I'm using data from a DEM layer, which contains information about elevation. I used this information to obtain slope ...
3
votes
1answer
201 views
Field sampling design: stratified random or transect?
I am trying to understand the impact of scientific activity in a remote polar environment.
I have five locations in different parts of the region, where historic huts were placed for a couple of ...
3
votes
1answer
320 views
Stratified sampling with a point and polygon layer
I need to perform a stratified sample in the following context.
I have two layers; the first is a point layer (which consists of dwelling centroids.)
The second is a vector layer of polygons with ...
1
vote
0answers
864 views
How to Create Random Points Within a Polygon (Vector Layer)
I have a vector layer that covers a few acres of land, with the buildings cut out (so essentially just the soil in the area). I want to generate points within this defined area. Later, I will use my ...
0
votes
0answers
65 views
Sampling Points and Areas around them
I have some coordinates in QGIS. I want to sample the values corresponding to those coordinates on a layer. I know that I can do that for the exact point using 'Point Sampling Tool'. Is there also a ...
2
votes
2answers
628 views
QGIS Point Sampling Tool: Invalid layer
I am completely new to GIS, and am trying to extract data from PRISM Climate data.
I used the Point Sampling Tool in QGIS, but faced the following error:
The new layer seems to be created, but is ...
2
votes
2answers
646 views
Stratified sampling from point data in ArcGIS Desktop?
I have 8000 points with a zipcode number.
Actually those are tweet points talking about zipcode, so multiple points have same number (e.g. 300 points with zipcode 32,805).
I want to get 800 sample ...
1
vote
0answers
154 views
How to properly address autocorrelation for logistic regression of spatial data
Background for the Model:
https://stats.stackexchange.com/questions/268201/how-to-increase-mcfadden-score-and-choose-proper-predictor-for-binary-logistic-r
Data I have:
Forest loss points
Forest ...
