Tagged Questions

A density map depicts a number of objects per unit area.

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0
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0answers
25 views

catchment delineation

I am trying to use qgis to delineate between three sub-sub-catchments. I have contour shape file of 20 meter height. Sub-catchment is about 12 square kilometers area but consist of three ...
8
votes
1answer
226 views

How to create a Human Trafficking Heatmap in QGIS?

I'm trying to create a heatmap with about 325 points distributed around the city of Houston. (FYI Houston is a major human trafficking in the US: a title shared with LA and Atlanta depending upon ...
1
vote
0answers
38 views

how can i plot news stories to show how many stories include each country on a map of the world

We have a table that shows the number of news stories that include particular countries over a set period of time there are three news channels that we have this data for and we would like to show/ ...
1
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0answers
86 views

How to calculate the density of settlement per 100 square kilometers?

I have a point shapefile representing settlements. I want to calculate the density of settlement per 100 square kilometers. Should I use point or kernel density? I am working with ArcGIS. Is there any ...
7
votes
2answers
493 views

How to create a heat map or density map from stacked polygons in ArcMap 10

I have a polygon shape file that has many overlapping features. Each feature represents an area used by polar bears. So some of the polygons overlap and some don't, and there are separate clusters of ...
6
votes
2answers
69 views

summing up over an area based on a distance related function

Through a field study, we learned that the density of a bird species in the forest was related to the distance to forest edge: ln(density) = 1.89*(distance to edge) + 0.34 Now, for any forest ...
5
votes
1answer
138 views

Finding nodes with QGIS

As part of work in statistical mapping for school, I need to use QGIS to find the spatial extent of commercial nodes. A node is defined for this exercise as a zone of 75m in diameter where the ...
2
votes
1answer
172 views

How to Calculate Utilization Distribution Overlap Index (UDOI) in ArcGIS 10?

I was wondering if any of you happen to have any information on how to calculate the Utilization Distribution Overlap Index (UDOI) in ArcGIS 10? If I understand it correctly the UDOI takes two kernel ...
3
votes
2answers
104 views

Determine density or cover from a raster layer that has been clipped by a polygon

I am a very new GIS user using ArcMap 10. I have a raster layer of tree canopy that I have clipped so that the layer is in a polygon that is a circle with a 2km radius. I have done this for four ...
5
votes
1answer
198 views

How to produce density map in square kilometers?

I have a shp file with the location (lat, lon) of lightning spatial distribution. I want to produce a density map of lightning occurrence per square KM. I used density point function and I don't know ...
5
votes
2answers
120 views

How to redistribute population data using Python in ArcGIS?

I am trying to redistribute population data from census centroids among to housing density.Would you please help me to do that? I do have census area centroids (points) and the boundaries belong to ...
4
votes
0answers
163 views

Spatial join to kernel density / kernel density with polygon/point output in Arc

I'm looking for a way to join polygons to a density function for some other feature of interest. Current workflow make density raster from feature set of interest, using point/line/kernel density ...
10
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6answers
453 views

How do I make a heat or Choropleth map that uses polygons in QGis?

I've been playing around with the heatmap plugin for QGIS and I am wondering if it is possible to make heatmap with using a similar plugin/tool that uses polygons as well as points? I would like to ...
2
votes
1answer
66 views

V.kernel not working correctly in grass-6.4.2

I am using grass-6.4.2 for generation of heat maps of crime data. For testing purpose, I created a vector layer from my places shapefile which is a point data.The places shapefile contains more than ...
6
votes
2answers
196 views

How do I compute v.kernel maps in less than 16 hours?

I am using the GRASS GIS 6.4.2 bundled with QGIS 1.8.0, using a PostGIS dataset exported via v.in.org.qgis from QGIS, to create kernel density maps. The layer has 738,288 points. My problem is the ...
7
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3answers
240 views

Is population density considered continuous data and why?

Population counts are typically referred to as discrete or quantitative data. Why is population density a continuous data type when it is typically measured for aggregate areas such as census tracts ...
13
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6answers
1k views

What's the best way to produce a density map from weighted points in QGIS?

I'd really like to repeat the functionality of the ArcGIS Kernel Density tool - how could I do that? I would like to limit answers to easy-to-install free-and-open-source software – i.e. QGIS ...
8
votes
3answers
283 views

How to identify “true arcs” in Arcmap?

This is really annoying: the only good way of creating circles in ArcMap is using true arc, (compound curves) but I need to convert those to vertex (densifying) because of a compatibility problem. I ...
2
votes
0answers
117 views

kernel density with Grass-Qgis

Hello I am studying the use of GRASS GIS within Qgis and I need a little help with the understanding of the v.kernel module. I didn't find any human help within the manual (very cryptic) This are my ...
0
votes
2answers
189 views

How to densify a polyline according to a specific length? [duplicate]

Possible Duplicate: Add vertices to lines I am using QGis 1.8.0 I would like to densify a polilyne according to a particular length of segment (ex. 200 m). I know it is possible with other ...
5
votes
1answer
157 views

Adding kernel density output to map with ArcPy

I am trying to emulate the behavior of the Kernel Density tool from the ArcMap 10 GUI in a script; in other words, I want to calculate the density of a dataset, and add the visual result to a map. If ...
8
votes
1answer
485 views

What type of kernel density function does ArcMap use?

I know that there are several types of kernel density functions, such as uniform, cosine, Gaussian, etc. I was just wondering which one the "Kernel Density" functionality in ArcMap 10's Spatial ...
5
votes
1answer
959 views

How to do Kernel density analysis in QGIS 1.7?

Do someone have some suggestion? We would like to tray Kernel Density analysis as we did with ArcGis using QGIS?
4
votes
1answer
620 views

calculate building density in ArcMap

I have two questions related to calculate building density. I need to calculate the building density in a map which Data is in shape format. The buildings and the area are in two different layers. ...
4
votes
1answer
184 views

Finding intersection density for weighted lines connecting points across the continental USA

I'm working on an one-time problem that I'm hoping to solve with a computer program using free GIS libraries (preferably for VB.Net, C#, or Python... Java or C/C++ could work too). Alternatively, I ...
5
votes
1answer
283 views

How to calculate Line Density in QGIS?

I have a map of fracture distributions over an area and I would like to calculate the density distribution of fractures that intersect a moving window with a specified radius. Is there a way to ...
3
votes
2answers
110 views

How to find the distance within which a set percentage of features fall?

Someone asked a question earlier about finding the number of features within a certain distance of another feature in ArcView. I have the opposite question: is there any way, in ArcGIS 10, to find the ...
4
votes
2answers
299 views

What is the highest resolution of population density data that I can obtain for USA freely?

Ok so as far as my understanding goes the most high resolution dataset available that factors in many other things (other than Census data ) at a 1X1 km resolution is Landscan data created by Oak ...
8
votes
1answer
1k views

Dot Density Maps in QGIS?

Is there a 'friendly' way to create dot-density maps, where a polygon attribute data defines the number of dots (e.g. 1 dot = 100 ) using QGIS 1.7+? I say friendly because after a couple of hours ...
3
votes
2answers
2k views

Interpretation of ArcGIS Kernel Density legend parameters

In ArcMap 9.3 I've used Kernel Density to map various incidents, but the resulting shapefile doesn't display any units of measurement. Is there a good, not-to-technical source that would explain in ...
6
votes
1answer
265 views

Normalizing and adding kernel density rasters

I have 4 years of road kill data for one road, though each year has a different sample time frame (i.e. May-June vs. April-October) and therefore each year has a different number of surveys and totals ...
1
vote
1answer
144 views

Represent multiple work visits to the same location in ArcMap?

How can I get ArcMap to summarize and display multiple feature records for the same address location?
6
votes
2answers
1k views

Spatial statistics tools : clustering analysis on raster data

I've an apparently simple problem, but i can't find a clear methodology to use. I'm tasked to delimit "urban areas" by vector convex polygons, using the Gridded Population of the World dataset from ...
0
votes
0answers
150 views

Is there a tool that tells how many features there are within a set distance in ArcView?

I'm looking to create a raster, in ArcView, that represents how many features (either points or polygons) are within a certain distance from any given location within a study area. I know there must ...
3
votes
2answers
486 views

interpolating values within a certain distance of points

Let's say I have a set of points representing bridges. I want to create a kind of "heat" map that would highlight areas within my study area that has many bridges in good or bad condition. I have a ...
11
votes
1answer
908 views

How do you use GRASS's v.kernel?

I am flummoxed on how to use GRASS's v.kernel. I have a vector layer of around 2.5 million points. I want to make a heat map using v.kernel to show concentrations, since I have variable instances ...
5
votes
3answers
783 views

How to interpret GRASS v.kernel results?

GRASS manual reads: v.kernel - Generates a raster density map from vector points data using a moving 2D isotropic Gaussian kernel ... Ok, but how do I interpret the results? I understand that ...