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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1answer
31 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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15 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
45 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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28 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 ...
2
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1answer
76 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
39 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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0answers
50 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
28 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
249 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
121 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
169 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 ...
2
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1answer
291 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
43 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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0answers
45 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
18 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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68 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
399 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
75 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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0answers
156 views

How to solve Python error for raster analysis interpolation nearest neighbor in QGIS [closed]

I am trying to interpolate temperature values into a raster using QGIS 2.18.15 in Windows. I need the output file as a GeoTIFF (.tif) file. I have my input for temperature already in a shapefile, but ...
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1answer
23 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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0answers
358 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 ...
2
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0answers
346 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
217 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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0answers
53 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
513 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
68 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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0answers
22 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
19 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, ...
3
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1answer
71 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
989 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
181 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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0answers
80 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
1k 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
262 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
428 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
65 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 ...
3
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1answer
519 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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2answers
339 views

Analyse points within buffer [closed]

Quite new to using GIS and have a (probably very simple) question. I want to see if there is a greater occurrence of a species around a certain feature. i.e. is there a greater density of a species ...
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0answers
97 views

How to do regression analysis in SAGA for topographic correction

Currently I am trying to do the topographic correction using C-Correction. I would like to know if there is a way to do the regression analysis between L (uncorrected reflectance of each band from ...
3
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2answers
652 views

Rose diagram of direction values of polyline vector layer

I have a vector layer of polylines with a set of multiple lines having length and bearing (azimuth in plane). I need to make some statistics on these lines, including the construction of rose diagrams ...
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0answers
99 views

How can I analyse the visibility of the urban area in ArcMap? [closed]

I want to analyse the visibility of the urban area using ArcMap. I saw the image below and I want to have the same output. Can you explain the process and steps to obtain this output?
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1answer
414 views

ArcGIS Combine Fuzzy Membership and Weighted Sum

I would like to combine the workflow of fuzzy membership and weighted overlay for a suitability analysis and would like to ask if this is "allowed" scientifically. I have severeal criteria, some ...
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1answer
147 views

Tutorial for raster analyse in ArcGIS or QGIS [duplicate]

Does anybody know where I can find some good tutorial for raster analyse in ArcGIS or QGIS?
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0answers
502 views

How to delineate a zone of slope break

I have a DEM of a region and want to delineate about a half-mile region at the base of hills (e.g. an area where the slope changes from steep to shallow). I ran the slope analysis tool and it kinda ...
2
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1answer
73 views

Temporal analysis in GIS - Tool to identify the jump points

I'm searching for a tool that help to analysis spatial temporal data in GIS. This is my problem: I have a database with a set of 170 georeferenced ovitraps (traps to catch mosquitoes eggs) with the ...
3
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2answers
439 views

Proportional Coloring within polygon for multiple variables

I'm new to QGIS and I am doing some demographic analysis of Ethiopia. I have a vector map with each of the country's administrative zones: Within the attribute table, I have data for religious ...
3
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2answers
669 views

Limit radius of ST_Clusterwithin (PostGIS)

I have a set of over 800k points and I am looking to cluster them within specified circle radius. I need them to be clustered to maximise the number of points within the circle. This is to model how ...
2
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1answer
77 views

What Algorithms to use for Levee breach Analysis?

I have a (relatively) High resolution DSM of the Country side, and want to figure out the extent of area that will be flooded if the Embankment/levee fails at a a given point. Something like this: ...
2
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1answer
430 views

Road Graph in QGIS

I am learning transport related analysis in QGIS. While using Road Graph (Shortest Path), after giving the specifications, the shortest path panel is not being displayed. Could some one help?