Measuring data values at specific, discrete locations.

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2
votes
1answer
51 views

Deciding how many random sampling points needed for specific area?

I have a study area (forest) around 25he. I would like to randomly have sampling points (center of the sampling plots) there. How many points (plots) I need in related to the area of my case study? is ...
4
votes
1answer
59 views

Plugin not available : point sampling tool

I installed the QGIS Standalone Installer Version 2.14 (64bit). I created a map in the program called QGIS Desktop 2.14.3 with GRASS 7.0.4. I need one tool from Plugin : Point sampling tool. The ...
3
votes
0answers
28 views

Sample Design for Kriging

I am taking soil samples on an agricultural plot and will be using the results as input to create a semivariogram for kriging in ArcGIS. This plot features raised planting beds in which the test crop ...
1
vote
0answers
38 views

Efficiently iterating through raster calculations with Rasterio or GDAL

I've got a very slow and round-about way to currently do this, but I struggle with the general concept of using windows in raster calculations and how to apply an affine or geotransformation between ...
3
votes
3answers
132 views

Point attribute from underlying raster data TIFFTAG

I have a layer of manually set points in qgis that have the following attributes at the moment : id, lat, long Additionally, I have a number of different overlapping raster images (sattelite data) ...
2
votes
0answers
28 views

Sampling raster by line in QGIS

I am quite new to GIS, and was wondering if you might be able to help me out? I have a raster layer for gradient as well as a line created from GPS tracking points(using the point connector tool). Is ...
1
vote
1answer
63 views

Getting NULL-values when point sampling USGS (SRTM 1 Arc-Second Global) grid (QGIS 2.8.2)

I use the Point Sampling Tool in QGIS to transfer gridvalues (of DEMs) to point features. This goes well with grids from f.i. MapMart (SRTMHARRIS_DEM), but I get only NULL-values when using grids from ...
1
vote
0answers
118 views

Zonal Statistics for multiple rasters

I'm trying to create a timeseries of raster data (one layer per year) by polygon (Administrative regions). Is there any way in QGIS to perform Zonal Statistics for multiple years (without having to ...
3
votes
1answer
85 views

Spatial sampling design

I have some plots of land spread across the landscape. Sometimes a parcel is subdivided in different sectors. For each parcel (and, in case of subdivision, for each sub-section) the quality of ...
1
vote
1answer
284 views

Receiving NULL values from Point Sampling Tool in QGIS

I am using QGIS 2.8.2. My project includes a raster layer of flow depth representing the output from a flood simulation (.DAT file). It also includes a vector layer of points representing the ...
1
vote
0answers
136 views

Generating regularly spaced sample points in qgis based on ratio of area

this is my first post on Stack Exchange. The question I have involves generating sample locations in irregular shaped polygons in qgis. In my situation, there are often many polygons in one shapefile ...
0
votes
1answer
98 views

Sampling one shapefile with polygons of another using R?

I have two shapefiles that partially overlap. One (the bigger one) consists of several polygons which represent fields I am interested in. The second, is a rectangular shape that overlaps about 30% of ...
2
votes
2answers
291 views

Creating Random Points that respect minimal distance across features / strata using ArcGIS for Desktop?

I have a shapefile with multiple polygons in which I want to distribute random points. Each polygon should contain exactly one point. The minimal distance between the random points should be 200m. ...
2
votes
1answer
570 views

How to create one random point per grid cell? (i.e., systematic sampling with randomly placed points)

Using ArcMap, I have used the Fishnet tool to create a grid of 1km squares. I am looking to create random points so that there is one (randomly placed) point per grid cell, with a minimum distance of ...
0
votes
1answer
79 views

selecting a random sample of parcels

I am faced with the following issue. I got a raster map showing the position and extent of land parcels within a 35 sq Km area. The number of parcels is about 200. In anticipation of the following ...
3
votes
1answer
844 views

How to generate random points with minimum distances between points in multiple polygons

I am looking to create random points for a random stratified survey. There are three different categories being surveyed; for each, I have a single shapefile, each containing a number of polygons. I ...
2
votes
1answer
1k views

QGIS 2.6 - Point Sampling Tool plugin producing empty shapefile

I use a DEM file (*.tif) and a points layer. My need is basic : getting the Z value for each point by extracting them from the DEM. Both layers correctly opened with QGIS 2.6. The DEM returns a Z ...
2
votes
1answer
54 views

Applying distance/area dependent procedures in geographic coordinates over large areas?

I'm currently doing some niche modelling with data in geographic coordinates spanning all of Latin America. I am using R for my analysis. Some of the tasks I have to perform are area/distance ...
1
vote
2answers
752 views

Using Spatial Analyst Sample tool

I have a bunch of rasters and a point file. I need the information from ll the raster files to be added to my points. My usual workflow is to use the Spatial Analyst sample tool. It works fine and ...
1
vote
1answer
401 views

Do I need to run regression in each samples separately?

I'd like to do smooth NDVI image by regression analysis; response of time series NDVI image to Julian date to represent the seasonal changes in NDVI as a function of Julian day. The time series NDVI ...
1
vote
1answer
32 views

RasterStack extract() for duplicated dates

I have a a Large RasterStack of temperatures and a 10570 points in a Large SpatialPointsDataFrame and I'm using extract() to assign the temperatures to each point in R. sub<-stack(temp@layers[...
0
votes
1answer
219 views

Point-sampling rasters using R? [duplicate]

I need to be able to sample many raster files (imported from GeoTIFFs) using a previously defined set of spatial points, using R. What's the best way to do this?
0
votes
1answer
932 views

how to choose stratified random sample on multispectral image

I'd like to choose random samples from multispectral image according to each Land Cover image. The multiband image has 70 bands representing land surface temperature data from MODIS. Land cover image ...
1
vote
0answers
299 views

GPS data cleaning - Sampling of track data

I have gotten a fairly large polyline-dataset of GPS-recorded tracks. I'd like to have a sample along the tracks for different variables. The problem is that the data has overlapping tracks. This ...
2
votes
1answer
471 views

Getting null values using Point sampling tool in QGIS 2.0.1

I would like to obtain the information of a raster layer at some points. Apparently the Point sampling tool does the job. I have used this tool, and all the raster values extracted at specific points ...
25
votes
4answers
4k views

What are the benefits of hexagonal sampling polygons?

I am always on the lookout for useful methods to sample or partition study areas (usually in the form of raster datasets) into smaller units. Recently, I read an ESRI blog post about a new tool for ...
7
votes
3answers
1k views

R - How to sampleRandom() from large raster without NA values

I have a number of vary large rasters which need to be randomly sampled with the return value being a matrix of x, y, and value. The raster package sampleRandom(raster,n, na.rm=TRUE, xy=TRUE) will do ...
0
votes
2answers
100 views

Error point sampling tool

I'm usig QGIS 1.8.0 and I did some interpolations. Now I want to do some sampling with the point sampling tool but I keep getting this error (I attach a picture of the error message). Does anybody ...
2
votes
1answer
389 views

Stratified Random Sampling by ID in QGIS?

I've been playing around with the Random Points tool in QGIS to realize stratified random sampling, but I'm running into a problem where I want my strata to be based on a polygon ID, not each ...
0
votes
1answer
161 views

How to add information to an attribute table?

I'm working with qgis 1.8.0 and did the following: 1.-Divided my shapefile into 830 features (small rectangles). 2.- Added to my shapefile several points containing weather information using the "add ...
5
votes
0answers
101 views

Estimation of values for unsampled points

I want to measure biomass on a coastal mudflat. I can only access points inside the polygon. Are there any methods available that would allow me to estimate values of the points outside of the polygon,...
2
votes
1answer
729 views

random sampling from spatial points in R

Can anyone help me out on the best package to sample from a spatial point dataset? My dataset consists of a list of positions inside a region, and for each point I also have the name/number of the ...
3
votes
1answer
1k views

Extract multi values to point error

I am trying to extract values from my rasters (slope, aspect, landcover etc.) for my animal group locations. I used Spatial Analyst > Extract Multi-values to Points, but when I look in my attribute ...
14
votes
2answers
5k views

Minimum number of samples for kriging interpolation

I get some data with number of specimens with a request to interpolate it using kriging method. After some investigation it appeared that kriging results (performed in ArcGIS Geostatistical Analyst ...
7
votes
3answers
5k views

Extract Overlapping Polygon Data to Points

I have a polygon data set of corn yield collected by a combine. However, as the combine drove through the field, there was slight overlap between passes, leading to overlapping polygons within the ...
3
votes
0answers
377 views

Getting coordinates of pixels

I want to compute an area of certain object on a picture using Monte Carlo method. The picture shows some shape on white background. To do so I figured out that I'd get the coordinates of non-white ...
5
votes
1answer
2k views

Is there a source for free CSV files with geo data and other desired fields? [closed]

I'm writing some software components that process geospatial data. The input data is a CSV with general columns (e.g. name) and geo columns (e.g. city, lat or zip). I would like to test these ...
3
votes
1answer
479 views

Extract pixel value for corresponding gps location in R

I have animal gps data with several locations for each day and regular gaps of several days when no location of the animal was recorded. Additionally, I have satellite data in intervals of 16 days. I ...
14
votes
2answers
2k views

How much sense does it make to average (lat,lon) samples in order to increase 2D accuracy of a GPS location?

Several GPS applications, like this one, or this one, acquire multiple (lat,lon) samples of a given location, assuming that the GPS unit is not moving, and then take an average of the samples in order ...
7
votes
1answer
2k views

What sampling tools are available in QGIS?

I'm looking for a tool to generate a stratified random set of points within the boundaries of a polygon layer. In ftools 0.6.1 there is a tool which almost does what I need, but misses the stratified ...