Questions tagged [analysis]

The process of extracting geographic, statistical, geometric, or scientific information from one or more related collections of GIS features and data.

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33 views

Calculate Percentage population from Vector Grids

I have a vector grids layer of population (shapefile). Each grid represents population in that grid and have the following attributes: Area Population I want to calculate and display the percentages ...
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20 views

My service area polygons are not right, look more like road buffers

I have included a screenshot of my settings and what one of the polygons looks like. I have this set to approximately 10, 20, and 30 mile service areas and this entire segment is only about five miles ...
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31 views

Analyzing NDVI rasters with same dimensions but different extents with Raster Calculator

I have drone sourced remote sensing imagery (NDVI) of a trial site set up to measure yield response to varying nitrogen (N) rates. The trial includes N rates ranging from 0 to 600 kg/ha. The trial ...
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10 views

QGIS Centre Pivot Wheel Vector Height Intersection With Raster

I am trying to visually display a centre pivot irrigator against a DTM Raster file to check terrain clearances in QGIS. I have a 1m DTM Raster and polygon/and line vector files of the pivot wheels. ...
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10 views

ArcGIS Online Business Analyst Shared Datasets Dynamic or Static?

I am testing out a trial period of the ArcGIS Online Business Analyst extension and I have successfully created a business list points data layer that I have now shared in my ArcGIS Online ...
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53 views

Intersect_analysis in ArcPy “The table was not found.”

Is there a bug in ArcPy? I have two features I want to intersect in a feature data set using ArcPy (this is a small part of a bigger program). Let me preface this by saying that when I do this in ...
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27 views

Creating Least Cost Path with cost distance analyse

I'm trying to create Least cost Path analyse between two points in QGIS. I had DEM and from this I created Slope with various elevation values. Then I made two points with different layers. Both of ...
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16 views

Service Area - Not taking into account of all network

I'm trying to work out an 800m service area from a station. However, QGIS is not taking into account some of the network lines. The yellow colour highlights the network that should be included in the ...
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1answer
95 views

Difference between ST_Simplify function in PostGIS 3.0.0 and PostGIS 2.5.3

Faced such a problem (or maybe it's a bug). I get different results when using the ST_Simplify function in PostGIS 3.0.0 and PostGIS 2.5.3. There are source data that are simplified by using a query: ...
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17 views

When carrying out spatial point pattern analysis on my point files I get an error for standard distance

How to fix an error with standard distance in spatial point pattern analysis. When performing spatial point pattern analysis QGIS 3.4 is only carrying out the mean point calculation correctly and ...
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17 views

Average raster value between points

I have a rasterized stream network, with point (species presence) data overlaying it. What would be the basic workflow for determining the average cell value between all possible combinations of ...
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42 views

Spatiotemporal analysis with polygons and points

In QGIS, I have a dataset of burned areas (polygons) and lightning strikes (points). In both datasets, I have the date of the fires, date of the lightning strikes, latitudes, and longitudes. However, ...
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1answer
279 views

Least Cost Path Analysis in QGIS?

For my Bachelor's thesis I try to reconstruct a road betweeen two ancient cities. One method I'd like to try is least cost path analysis with QGIS. I've worked with QGIS before, but mostly only ...
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1answer
38 views

2 raster files, find suitable area [closed]

I have done this with vector before, but now I have 2 raster layers: 1 raster layer that refers to land use: urban, forest, water, agriculture 1 raster layer that was classified in 3 classes for ...
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21 views

Is there any method to generate the minimum number of intersecting grid squares to a polygon?

I know I can generate a group of fixed sized intersecting square grids for a polygon using the bounding box of the polygon and generate gird squares on that and keep those, which are intersecting with ...
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1answer
63 views

Assign points within 150 meter buffer of each other the same unique identifier?

I have a bunch of points on a QGIS map. Each point is a unique sampling event. However, some of these points have been sampled multiple times but there is no common identifier in the attribute data to ...
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34 views

Vector to grid - Computing statistics by grid cells

I have a vector point data from drifting buoys (speed, direction, sst, slp) that I want to analyse in a grid. What are the right tools for this? Example of my points data below. Each point has the ...
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1answer
141 views

Do Not Filter vs Ignore Invalid Geometries

In QGIS 3, What's the difference between "Do not filter (better performance)" and "Ignore invalid geometries"? Both can be found at Settings > Options > Processing > General Both are options to ...
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1answer
56 views

Viewshed Analysis for Custom DEM file [closed]

I am new to qgis and trying to do 2 things. My objective is to have an accurate viewshed analysis at the end. But my DEM file is of poor resolution. I do have a shapefile with building height ...
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67 views

How to automatically compare two aerial photographs with a GIS with regard to certain features?

At present, we are trying to automatically record the new use of land by buildings by systematically comparing aerial photographs (e.g. 2007 farmland -> 2008 warehouse). For this purpose, high-...
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1answer
29 views

Selecting Different points in 2 different layers

I'd like to make an analysis on points. I've 2 layers they have house numbers as an attribute. What i'd like to do is compare these 2 layers and select the different ones. Geometrically there are ...
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1answer
606 views

Network service area - QGIS

I want to check if schools from my hometown are accessible for students who use public transportation, so I need to perform this analysis in order to see if the schools are located in the range of ~...
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1answer
395 views

Count points in polygon (weighted) for multiple attributes in QGIS 3 in one go

Is there a way to count weighted points inside polygons for multiple attributes at one time? I can count weight points (below) for an individual attribute, which creates a new polygon layer with an ...
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1answer
409 views

Stereoscopic Interpretation on QGIS [closed]

I would like to know if anyone has worked with stereoscopic analysis (e.g extracting features such as drainage, forest an so on) using the following softwares: QGis, gvSIG, ILWIS or MicroImages TN ...
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1answer
491 views

Count points in polygon (weighted) in QGIS 3

In QGIS 2 you could perform a weighted point within a polygon layer using Processing toolbox > Vector Analysis > Count points in polygon (weighted). I could well be missing something, but I can'...
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1answer
69 views

Analysing landuse data in a buffer layer

In my project I want to analyse the landuse around some points within a certain radius. So I created a buffer around my points but I have no idea how QGIS could probably tell me what different ...
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57 views

Network Analyst takes so long

Is there some kind of limitations of number of features when we work with Network Analyst in SDE ? My net has 170.000 features, is it a problem ? Because it take at least 6 hours to finish the "Build ...
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1answer
22 views

How to define the angle of points on slope?

I have point data set and DEM and my task is to identify how many points are falling on the slope of more than 40 degrees. How could I do this in ArcMap?
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89 views

Using the height of river to approximate its extreme flood boundaries - terrain analysis in QGIS?

Using QGIS I'm trying to analyse an area/DEM with this criteria: - heights 10 meter above the river-centerline in both sides of river. I can do it with the calculation of contours (2m) from DEM and ...
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1answer
706 views

Calculating population size from raster layer using QGIS?

Is it possible (using QGIS) to calculate the population size from a raster layer within a certain area? For example: I have a population density raster layer (100x100 grid cell) for South Africa, ...
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1answer
100 views

Make rasters to show the extent of certain data values

I'm trying make a raster of the area between 5 and 10 thousand feet in Colorado. I have DEMs, and I'd like to make a raster where all the area in this range is a value of 1, and the area outside the ...
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2answers
28 views

Private Surface Water Mains In Between Public Mains Analysis

I am working in a geometric network of a surface water (stormwater) system. We have both public and private assets (pipes/mains, manholes, inlets/CB's, etc.) in the network. I am doing a bit of QC on ...
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549 views

Standard Method to calculate Average Moving Speed from Times & Coords?

...I wasn't sure if this question was best suited to GIS, SO or Math, so after reading GIS Topics I decided to ask here, but I'll relocate if necessary... :-) I'm working on automating various ...
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0answers
405 views

how to calculate cumulative cost of movement, accounting for wind direction, in R?

I am trying to reproduce the calculation of the duration of sail-powered navigation as described in an academic article (http://www.tandfonline.com/doi/full/10.1080/15230406.2017.1403376), but using R ...
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1answer
240 views

GWR with dependent and explanatory variables in different files

I have a point shapefile (let's say A) with pollution measures (let's say Y). My hypothesis is that pollution at theses locations is primarily driven by nearby industrial units and not by activities ...
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59 views

Road Network Accessibility

I am working in qgis with 3 layers: one is road network and other is hospitals and locations of accidents , later two layers are as points, I want to figure out what accident location (points ) are ...
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2answers
885 views

Determining if polygon falls within another polygon using QGIS?

How can I determine if a certain polygon falls within another separate polygon using QGIS?
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1answer
81 views

network analysis that includes user defined nodes

I want to make network analysis using python. I want that user must be able to select point of interests and calculated route must contain that points. For example between start and end nodes user, ...
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25 views

Are tesselation patterns an effective way of covering a shape?

I am using Facebook place search to explore business pages on Facebook. If I input a longitude and latitude into facebook's GraphAPI, I can search within a given radius for facebook business pages. ...
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0answers
22 views

Cutting a line by a list of varied percentages along [closed]

Does anyone know a way to cut a line at specified percentages along that line? I know you can do this in ArcGIS if you have a specific percentage in mind, but I want to do it at varied percentages (5, ...
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1answer
74 views

Why does my RAM cap out around 150 MB when doing the Distance Matrix analysis in QGIS?

I am currently trying to determine the 2 nearest points for a database of 8 million people against 425 locations. I have 2 csv files uploaded into QGIS one with a unique number for 8 million people ...
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2answers
1k views

Moving GPS points with distance + bearing [closed]

I have a list of 73 GPS points that represent animal observations. Each point also lists the bearing (angle in degrees) and distance from the observer to the animal. Instead of displaying each point ...
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1answer
209 views

solar potential analysis of 3d city model [closed]

I am looking for a free application/tool/plug-in to conduct solar potential/irradiation analysis on a 3D city model. My intention is to know how much solar energy is delivered onto the rooftops and ...
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88 views

Is it possible to combine buffer zone analysis with time series analysis in QGIS?

There is a multitemporal analyzer in QGIS where it is possible to do a buffer zone analysis combined with time series analysis, where there are two layers an input layer and a target layer and the ...
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1answer
2k views

Classifying slope (flat, slope, steep, very steep) in QGIS? [duplicate]

I want to classify the slope of the DEM data, by dividing the slope by 4 classes: flat, ramps, steep, very steep. How to do this with QGIS?
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1answer
347 views

Using QGIS to find and calculate parts of polylines within polygon?

I've already got QGIS (2.18.2) to add an ArcGIS shapefile with polylines create a polygon which is a buffer region around a subset of the polylines in the ArcGIS file add a KML file with one polyline ...
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1answer
562 views

QGIS Calculating Line Lengths and Statistics

I am working through this tutorial: http://www.qgistutorials.com/en/docs/calculating_line_lengths.html In the tutorial we import a shapefile map of railroads,clip the data through a selection/...
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1answer
71 views

How to devise the time to cross a raster's cell knowing the speed of movement?

Let's assume I have a raster representing the speed of movement in Km/h, and the raster cell size is, say, 500m. Am I correct in understanding that, in order for me to calculate the time it takes to ...
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1answer
1k views

Shadow impact of building on certain area [duplicate]

I have done some research but was not able to find a solution to my task! What do I want: Pretty simple - I have a building and I want to know how its shadow is influencing a certain site at ...
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1answer
746 views

Algorithm or GDAL module to calculate LOS

I'm involved in a project using GDAL via python. We need to be able to calculate if, standing at point A it is possible to see point B, given a DEM. To clarify we do not need a viewshed algoritm, we ...

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