Geographic Information Systems

Questions tagged [spatial-analysis]

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A set of techniques for analyzing spatial data

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Frequency analysis of linestring using R

I have a data-set that consists of linestrings across different timestamps. I want to identify the segments that occur the most frequently. I import a set of JSON files to create the data.frame with ...
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1answer
37 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
38 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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1answer
31 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 ...
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1answer
43 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
49 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
129 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
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2answers
162 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
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0answers
39 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
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2answers
132 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
341 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
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1answer
71 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'...
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3answers
64 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
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1answer
134 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
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1answer
341 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
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0answers
23 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
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1answer
76 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
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0answers
211 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
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0answers
570 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
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1answer
146 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 ...
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2answers
177 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
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1answer
159 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
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1answer
212 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 ...
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0answers
336 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
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1answer
126 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
67 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
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1answer
524 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 ...
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2answers
520 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
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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
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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
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0answers
238 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 ...
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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
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1answer
123 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
37 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
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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
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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
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1answer
472 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
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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
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1answer
221 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
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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 ...
5
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1answer
184 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
206 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
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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 ...
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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
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1answer
158 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?
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0answers
39 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
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1answer
289 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
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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 ...

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