Questions tagged [spatial-analysis]
A set of techniques for analyzing spatial data
69
questions
0
votes
1answer
26 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
votes
1answer
40 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
44 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) ...
1
vote
0answers
105 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
141 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
34 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
111 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 ...
1
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0answers
305 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
66 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
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3answers
63 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
112 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
332 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
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0answers
34 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
vote
0answers
21 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
75 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 ...
7
votes
0answers
199 views
Computing the horizon profile given a DEM in python
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
535 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
138 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
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2answers
168 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
155 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
199 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
320 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
112 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 ...
1
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0answers
62 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
491 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
492 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
915 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
93 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
228 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
51 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
114 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
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0answers
36 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
51 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
463 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
73 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
219 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
74 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 ...
5
votes
1answer
180 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
204 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 ...
1
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0answers
27 views
How can I quantify whether locations of one 'type' are closer to one another compared to a second 'type'?
This might have an obvious answer but I'm new to GIS and can't seem to find the right technique... I've got GPS points for a bunch of households and have calculated the distance (in km) between each ...
1
vote
1answer
152 views
What is directed principal component analysis? [closed]
Is there any difference between directed principal component analysis and principal component analysis?
If yes how (which software) can I perform the first one?
0
votes
0answers
38 views
Common methods of area comparison?
I have a set of raster area results, that represent a prediction for a specific loccation. I would like to measure accuracy of two methods, given the actual values, estimate-A method values and ...
2
votes
1answer
279 views
Polygons within Polygons Spatial Analysis
I have a polygon layer of planning applications and I am wondering if anyone can give any advice and or has seen or written a blog post that might point me in the direction of creating relationships ...
1
vote
1answer
116 views
Looking for a data set of geo tracking for a group of users
I run a study on user commuting patterns and I need a data set where each line would be something like:
userID | Timestamp | lat | long
Then, I would like to analyze each user separately and derive ...
3
votes
2answers
1k views
How school catchment area analysis is done [closed]
In fact i am asking for the method and the data needed for determining school catchment area.Example is http://www.qgso.qld.gov.au/maps/edmap/.
Probable Prerequisites:
Catchment boundary must not ...
5
votes
1answer
684 views
How to find all points with certain elevation difference between them in QGIS
I have a point layer (xyz) and want to find all points that have elevation difference of 200m or more. I would like to then draw a line between each pair with the largest elevation difference.
The ...
0
votes
1answer
77 views
Vertical section of viewshed
How can someone make this vertical section of a viewshed analysis (e.g. in ArcMap)?
