Questions tagged [spatial-analysis]
A set of techniques for analyzing spatial data
77
questions
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12 views
Picking particular color(s) from Raster to generate new raster
I'm trying to pick just three colors from the raster I'm working with to generate an output raster. The problem is when I use the Image classification tool- Iso cluster unsupervised classification &...
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0answers
14 views
Comparing Geostatistical Interpolation Results based on statistical parameters
Using Geostatistical Analyst's cross validation results would it be wise to compare the results I am getting RMSE values for different interpolation techniques (e.g IDW, Radial Basis Function, Kriging ...
3
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0answers
23 views
Analyze length of loops on network
I am working on a hiking network. Basically it is a selection of roads/paths suitable for walking/hiking. Each junction of three or four selected tracks is numbered. Each track is a line that starts ...
1
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1answer
70 views
Splitting a polygon by multiple linestrings leaflet and turf.js
I am trying to implement an utility for land subdivision using leaflet and turf. I am not sure if these tools are the right ones for the task. I've got it right for most of the scenarios but sometimes ...
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0answers
19 views
Extract Census Blocks using Block Centroid that falls within Buffer in R
After creating buffer zones, I want to select a subset of Census Block IDs whose Centroids fall within the buffer zones. I have successfully built the data for all the Blocks and the designated ...
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0answers
43 views
Balancing multiple supply and demand locations in QGIS
I am looking for a way to balance supply and demand with respect to distance, between two vector layers in QGIS.
I have two vector layers 50x50m grid
Supply (The red negative values)
Demand (The ...
0
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1answer
58 views
Frequency analysis of linestring using QGIS
I have a data-set that consists of linestrings across different timestamps. I want to identify the segments that occur the most frequently.
I am using R to import the data from JSON files, create ...
1
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0answers
47 views
Overlapping area from data using QGIS?
I have a database containinig lots of data for each province. I'd like to know if there's a way to obtain areas of concentration of the phenomenon from the automatic overlapping of these data.
I hope ...
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votes
1answer
37 views
Buffer analysis of points, counting intersects of resulting polygons
I am using ArcGIS pro and this is the first time I've done something like this. I don't have a "proper" GIS background and have just been plotting point maps and choropleth maps.
I've been asked to ...
0
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1answer
63 views
What does first requirement for LISA statistic mean?
According to Anselin, a LISA statistic have to satisfy two requirements:
The LISA for each observation gives an indicator of the extent of significant spatial clustering of similar values around that ...
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0answers
56 views
Supervised Neural Network for site selection in GIS [closed]
I have a set (A) of geospatial raster data layers and a set (B) of point data.
(B) includes numerical values that indicate the "suitability" of the specific site with a rising value. I know that (B) ...
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0answers
173 views
Finding nearest distance between point and polygon layers in QGIS
I am using QGIS to undertake an analysis for a project.
This involves a polygon shapefile, which represents a boundary of a site, and a series of points which represents the location of parks.
I ...
3
votes
2answers
264 views
Find what polygons are not fully covered by union of polygons from another layer in PostGIS
I have two tables in a PostGIS database
>>> select postgis_version();
"2.5 USE_GEOS=1 USE_PROJ=1 USE_STATS=1"
One represents the country borders and another one is administrative ...
2
votes
0answers
45 views
Count the number of points of a multipoint-feature [duplicate]
I try to use the fieldcalculator in QGIS 2.18 to count the number of points of a multipoint-feature. Is it possible?
2
votes
2answers
181 views
Moving multiple points in batch using ArcGIS Desktop?
I have multiple parcel polygons and they all have one side touching the lake polygon. Each parcel polygon has a point inside which is now at the centroid of the parcel. I need to find a way to move ...
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0answers
400 views
Comparing speed of Spatial Analysis with GeoJSON versus shapefile in QGIS?
I have a large dataset that I want to perform spatial analysis on in QGIS.
Specifically, I want to perform a polygon intersection analysis between two polygon layers.
Given the size of the dataset ...
2
votes
1answer
75 views
Finding remoteness of point using QGIS?
I'm sure this shouldn't be as tricky as I'm finding it but does anyone know how you can find the 'remoteness' of a point compared to multiple other points in QGIS?
I have a shapefile containing 1000'...
0
votes
3answers
70 views
Seeking article on network analysis, connectivity analysis, and proximity related to routes and influence of stations? [closed]
Unfortunately I lost a document I had found on the internet, and I do not remember the title
the article was like a guide or recipe and it was in pdf format, and it was related to network analysis, ...
2
votes
1answer
172 views
Horizon line of a vector point from terrain raster - global mapper
Is there a possibility to calculate the horizon line of a point with global mapper, not the viewshed, but just a line (or polygon) joining all the furthermost points from A and are at the same time ...
1
vote
1answer
369 views
Analyze time series NDVI using bfast
I would like to study a trend of NDVI data for a specific time interval using bfast package.
For this final aim, I read about the necessity to convert my data frame into a time series object in R. ...
2
votes
0answers
35 views
ArcGIS Online spatial analysis
I am currently attempting to put together a web mapping application for a client through the AGOL web app builder. One of the layers in the application is a set of grid cells covering a large ...
1
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0answers
25 views
Dividing space into homogeneous connected areas [duplicate]
Is there an algorithm (or software) for splitting a map into K connected areas such that the within-area variance of some variable is minimised, and the between-area variance of that variable is ...
3
votes
1answer
84 views
Unexpected results with Raster Terrain Analysis Plugin
In QGIS 2.18.18 on Windows 10, I have downloaded the NASA file srtm_05_01.tif that is available at http://dwtkns.com/srtm. I use the Terrain Analysis Slope method on that file with the following ...
2
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0answers
44 views
Finding the optimal boundary polyline in QGIS
I am looking to find an optimal boundary line between two geographically separated sets of points (a vector layer with S and N points representing two genetic lineages within a species). I would like ...
8
votes
0answers
238 views
Computing the horizon profile given a DEM in Python [closed]
Can anybody orient me towards an open source Python script that computes the 360° horizon profile (azi + elevation of highest topography in eye sight) from a single point (x,y,z) on Earth (account for ...
4
votes
0answers
660 views
Emerging hotspot analysis (space-time patterns) in QGIS
I worked with crime data a while ago and was really impressed by the possibility in ArcGIS to detect significant hotspots and their development over time (Emerging hotspot analysis).
Does anybody ...
2
votes
1answer
161 views
Analyzing population within buffer using raster population grid
I have a set of points and a population grid that is a raster file (http://sedac.ciesin.columbia.edu/data/set/gpw-v3-population-density-future-estimates/data-download). I am trying to solve how many ...
1
vote
2answers
186 views
Coordinate systems for countries around Caspian Sea?
I'm trying to do spatial analysis of the Caspian Sea area and am not sure which projection to use for the countries around it. The Caspian spans multiple UTM zones and the countries around is are from ...
2
votes
1answer
171 views
Cluster analysis for different plant species with elevation, aspect, slope rasters using ArcGIS Desktop?
I am using ArcGIS Desktop.
I have a point shapefile for 5 different plant species and rasters (elevation, slope, aspect, canopy height). I am trying to find clusters for each species in terms of ...
2
votes
1answer
230 views
Use only points within a polygon for heat map in ArcMap?
I'm trying to make a point density heat map where the calculation for each cell considers only points inside a containing polygon and ignores those falling outside it (mainly because the outside ...
1
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0answers
353 views
Extracting a time interval from NetCDF-data in ArcMap Desktop 10.4
In ArcMap 10.4 (advanced licence) I have added a netcdf-file with EU-temperature-over-time data (time being every day between 1995 to 2016).
I just need the year 2010 from this data, but I'm still ...
2
votes
1answer
137 views
How does Spatial Join work under the hood?
I have a sidewalk_inspection points table and a sidewalk lines table. I want to do a spatial join between the points and the lines so that I can assign the ID of the nearest sidewalk to the ...
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0answers
69 views
Spatial Analysis Grouping/Clustering Question
If this question is incorrectly titled, I apologize; I wasn't sure exactly how to best phrase it. I'm working with my city's housing department to develop zones for building inspectors. One of the ...
5
votes
1answer
576 views
Why is QGIS points in polygon so slow when select is fast?
I'm looking at QGIS 2.18.9 and using a polygon to select points from a large point layer (file based tab file).
I wondered why the process is so slow if you use plugins or analysis options? I ask ...
0
votes
2answers
561 views
shortest distance between road and lake with PostGIS
I have a country-wide dataset with lakes (polygons) and streets (lines). For each lake I want to know the shortest distance to the closest street. (I do not necessarily need the closest street itself ....
2
votes
2answers
1k views
Cropping area of interest from raster file using Python?
I have been trying to crop out certain area of interest from a raster type .tif image format.
I was successfully able to implement that in R, but since shiny doesn't provide much for free, i have to ...
4
votes
1answer
96 views
Averaging points within a boundary
What I am trying to do is average a set of points with a separate boundary.
Each of the larger circles is a fixed distance around a sample point (typically the area sampled) with each of the ...
2
votes
0answers
255 views
Efficient way to analyze multiple (large) rasters against a different raster using numpy
The situation I have run into involves four rasters. I will try to explain each one and what it is for to help you get a better idea of what I'm trying to achieve.
One of the rasters has been ...
1
vote
0answers
52 views
Examples and physical materials that are helpful for teaching GIS principles [closed]
I am collecting some of the resources and materials that are helpful when teaching the basics of GIS to extend my current toolbox. Some of those I use myself when teaching introductory courses. I am ...
2
votes
1answer
129 views
Linking layers using conditional spatial queries?
I am looking at a drainage scheme where there are blockages in the system. The blockages are one layer. I then have a layer containing the main risk areas within the area and another layer that ...
2
votes
0answers
39 views
Working with intersecting polar grids
I'm having some trouble figuring out the best way handle some GIS data. I want to analyze pollution from specific sites at specific points. I have a list of sites I'm interested in all across the ...
2
votes
1answer
54 views
Cut polygon layer into a new subset by the boundaries of another polygon layer
ArcGIS 10.2.1
I have a feature class of wetland mapping. It is a series of various polygons, all irregular shapes and sizes.
I also have a parcel boundary feature class that is basically even sized ...
3
votes
3answers
2k views
Calculate areas of overlapping polygons from two shapefiles
In Why does intersect not calculate polygon areas? the answer is "The area values in attribute table are just random attributes in the eyes of QGIS. It is therefore perfectly normal that these ...
4
votes
1answer
481 views
How to calculate correct raster stats?
I've done a lot spatial analysis in ArcGIS. Then I decided to start to learn QGIS. I started with DEM analysis. But I found differences in statistics of DEM. ArcGIS correctly recognizes the lowest and ...
2
votes
0answers
74 views
Analysis method for Vegetation category change [closed]
I have a data set showing vegetation change over a 100 year period. The data is categorical (ie. Conifer, Deciduous, Mixedwood, Grassland, Shrub, Open Canopy forest, non vegetated). Each cell in my ...
7
votes
1answer
227 views
Categorising Point Clusters
I have a point dataset of solar farm locations. The points are grouped according to which substation they feed into (see below). I would like to test the hypothesis that electrical output ...
1
vote
1answer
76 views
QGIS - does a tool exist to calculate the (PostGIS) polygons containing a given point?
This is the converse of the analysis provided by the fTools plugin "Points in Polygon":
Given a single point and a list of vector layer polygons (PostGIS in my specific case), is it possible to list ...
6
votes
1answer
216 views
Tolerance in PostGIS
I am working with spatial data in land management using Oracle. The daily task is to perform spatial analysis: defining the mutual disposition of land plots borders, territorial areas etc. The ...
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0answers
212 views
different results :Slope analysis in qgis vs ArcMap
I want to make slope analysis on geoTiff. I am using ArcMap and qgis. But i get different results, but both are in degrees. I ArcMap i recive range from 0 to 42 degrees, but i qgis it from 0 to 17 ...
3
votes
2answers
2k views
Create largest circle (maximum radius) inside a polygon in ArcGIS for Desktop?
I am trying to create the largest possible circle inside a polygon including its perimeter and area size. I created via minimum boundary geometry the smallest possible circle outside a polygon (see ...
