The process of extracting geographic, statistical, geometric, or scientific information from one or more related collections of GIS features and data.
9
votes
4answers
510 views
Multicriteria Analysis : how to?
I have to do a multi-criteria analysis to answer the question : "which is the best lot to develop".
A few of the criterias are :
distance of the nearest bus stop (point layer with bus stops)
...
1
vote
1answer
189 views
How to calculate the Zone of Impact using OpenWind
After downloading OpenWind, I am trying to calculate the ZVI for a single Turbine. There is no documention regarding this from the developers.
At this point I just want to compare the output of the ...
7
votes
1answer
160 views
Looking for a trajectory similarity measure
For my final academic work I have developed a compression algorithm for GPS trajectories. I can estimate the quality of the spatio-temporal compression by computing the syncronized euclidean distance ...
3
votes
1answer
205 views
How To Determine Frequency Of Overlapping Polygons (Bounding-Boxes)
My starting point is a series of bounding box polygons, representing the extents of all the data sets in my inventory.
I am trying to produce an output grid showing the frequency of coverage over the ...
2
votes
3answers
1k views
Income data on a block level: how does a newbie do it?
I am a complete newbie at GIS data, and am trying to do the following:
Figure out census blocks in Miami-Dade (and several other counties) that have average household incomes > $75,000
Get the ...
4
votes
1answer
352 views
Analysing Information By Vector Grid
I have two vector line datasets and wish to compare the line lengths. While I have already compared the sum of the lengths, I'd like to conduct further analysis down to 250m, possibly lower.
I'm ...
2
votes
2answers
145 views
Spatial analysis? Two layers?
One is LandPlot and the other is Soils.
When I open the LandPlot attribute table I see I have 500 specific plots of land. When I open the Soils attribute table I see I have 5 types of soils (let's ...
2
votes
1answer
228 views
How to move a Point perpendicular from nearest Line?
I want to move Point perpendicular from nearest line or polygon, and the question is how to do that?
example, I have points (house number) near roadbed, and I don't want them to intersect roadbed ...
1
vote
1answer
186 views
Heat Map to find 10 restaurants, 10 retail, and 10 stores open after 6pm within 3 linear blocks
I would like to find where in the City there is a combination of 10 restaurants, 10 retail, and 10 stores open after 6pm within 3 linear blocks. What is the best way to do this? What data would I need ...
3
votes
1answer
158 views
Efficiently classify raster with irregular polygons
I have a project on my desk to classify an elevation model using different elevation breaks for each polygon in the area of interest.
In pseudo code:
FOR each polygon IN layer:
CREATE_MASK FROM ...
6
votes
2answers
188 views
Looking for advice regarding solar potential applications
I have the task of looking into whether it is possible to build a solar potential application which would inform the user whether a roof is suitable for solar panels and a brief report about the ...
7
votes
1answer
134 views
Analysis of GPS error
I'm wondering if there have been any studies which attempt to analyze or characterize GPS error distribution over different situations/conditions (e.g. surrounded by tall buildings/mountains, ...
3
votes
1answer
360 views
Is there an open source tool for both road network analysis and geocoding?
Is there any one open source software package that can perform both road network analysis and geocoding?
6
votes
3answers
399 views
Identification of consecutive points within a specified buffer
I have a point file, hourly relocations of an animal, and I want to be able to place a buffer around each point and calculate the number of subsequent points which are within the buffer zone. I am ...
8
votes
1answer
312 views
Open source GIS tool for mapping health data
Im looking for an open source desktop gis tool that can be used for visualization and exploratory analysis.
I want it to be interactive and perhaps display two or more maps at the same time to allow ...
2
votes
0answers
197 views
How to create a service area using both streets and buslines in the same network?
Hello,
I want to create a network analysis more difficult. Therefore, I want to calculate a Service Area around hospitals next to busstops. But: The network does not only consist of roads and ...
2
votes
1answer
374 views
How to integrate every single street into a network analysis?
This is my first question, but I solved problems before thanks to this great community!
It is also my first time working with a network analysis (ArcMap 10) and there are some problems which haven't ...
11
votes
1answer
173 views
What spatial analysis did the US Supreme Court review in the Perry v. Perez opinion?
The Supreme Court recently issued an opinion on Perry v. Perez which seems like it must have involved evidence based on spatial analysis. The L.A. Times reports:
The 9-0 decision set aside a new ...
3
votes
1answer
425 views
ArcGIS tool for indicating changes in land use
I have a couple of shapefiles in which there is some information about land use (polygons) such as water, forests, soils, buildings etc.
Each of the shapefiles represents a certain year of the same ...
5
votes
1answer
308 views
TRI, TPI, or Roughness
I am working on a site selection projection where I will be unable to perform any in situ observations. A key component of the selection process is the ruggedness of the underlying terrain.
I plan ...
4
votes
2answers
731 views
How to find the area of raster values within polygon zones?
I'm using ArcGIS 9.3 and I just can't seem to get this right - I've tried tabulate areas, zonal stats, converting to polygons, etc. I'm missing something somewhere.
I have a USGS impervious surface ...
4
votes
3answers
246 views
Vector Analysis: Determining area of county land mass without water features
Here are the layers that I have:
State / Province polygon file (With Area Field)
County / Ward polygon (with no area field), but all the polygons are within the state boundaries
Water ways for the ...
5
votes
1answer
226 views
How to find upstream - lateral and downstream zones around urban areas?
I've a DTM and a shapefile of built-up areas. For a fire risk model, I've to find (within a defined buffer zone) two zones around built-up areas: one that is above/higher and lateral and the other ...
6
votes
1answer
711 views
Nearest Neighbor calculation in PostGIS
I'm learning how to use PostGIS and spatial databases for analysis. What I am trying to do is perform a calculation to get the distance for the nearest polygon in a file, using the edge calculation, ...
5
votes
5answers
725 views
Spatial Join on two point featureclasses produces empty output featureclass
I have two point featureclasses that intersect each other. They are in the same projection and dataframe. The issue is, when I perform a Spatial Join the output point featureclass is empty. The file ...
18
votes
2answers
284 views
Ways of expressing geographic questions in machine readable form
A core concept of GIS is answering questions about datasets. From the point of view of a database; SQL with spatial extensions is a way of asking such questions. What other ways can questions be ...
7
votes
3answers
277 views
How to check if parcel is located by golf course
Is there any simple way for me to run millions of parcels through some type of script to see if a shape file parcel is on a golf course? For example if I have a layer that has all the golf courses and ...
7
votes
4answers
8k views
Extract coordinates of polygon vertices in ArcMap 10?
I've got about a dozen polygons in a feature class loaded in ArcMap 10, all in geographic WGS 1984.
How do I easily obtain the coordinates associated with each vertex of each polygon in that feature ...
7
votes
4answers
756 views
Spatial query tool for laymen
I know nothing about GIS, but I have what I think is a GIS problem. From spending a few hours googling my problem, I think what I need to do is perform a spatial query, but I'm not sure how to go ...
11
votes
2answers
153 views
How could I rate roads for scenic drives?
relative GIS newbie here.
I've been working on a personal project to rate roads on how nice a ride they'd be on a motorcycle. I wrote a Python program to work through road data in the TIGER dataset ...
8
votes
3answers
517 views
Temporal Analysis Tool: Seeking
I am looking for an alternative tool (proprietary or FOSS) that matches the functionality of Temporal Analyst for ArcGIS by DHI Software. The best I could get was the QGIS plugin Time Manager ...
4
votes
1answer
546 views
How can I calculate the vertical distance to the nearest water?
Summary:
I would like to create a raster where each cell contains the vertical distance to the nearest water (a decent approximation would be acceptable). The problem is that I'm not sure how to go ...
6
votes
4answers
1k views
GIS Project Workflow?
If you had to teach someone the key stages to a typical GIS Analysis project, what would be the best generic answer?
I would like to see diagrams to illustrate this point.
Do not think it requires ...
4
votes
2answers
615 views
Plugin for average distance from node to polyline in QGIS?
Is there a plugin available that will calculate this?
EDIT 1:
The red polyline is the average distance of the point to the black polyline. The red polyline is what I want to display. Alternatively, ...
10
votes
1answer
357 views
Spatial operators in R?
How can I do spatial selections or filters in R? I can do this in PostGIS using (e.g.):
SELECT * FROM mypoint, mypoly
WHERE ST_Within(mypoint.geom, mypoly.geom);
and it is similarly a piece of cake ...
7
votes
2answers
545 views
Is there a described GIS method for creating catchment areas based on nearest driving distance?
ie. a combination of Voronoi polygons with isochrones, so that the Voronoi polygons are based on driving distance instead of Euclidean distance. Is there a name or a described method for this?
6
votes
2answers
147 views
What multiplier would you use for calculating estimated population?
Given a number of address points in a given area, what multiplier would you use for calculating estimated population? I have seen 2.5 in a few places, but I was wondering what the generally accepted ...
25
votes
8answers
1k views
When is a 3D Visualisation in GIS Useful?
I can currently only think of two cases:
to visualise potential changes in a landscape, such as the effect of adding windfarms, or the addition of a new building to an urban area. However both these ...
11
votes
3answers
223 views
What practices are available for modelling land suitability?
I currently use a "classic" raster based approach of dividing a study area into cells. All input layers are converted to rasters at the same cell resolution and given a suitability rating.
A final ...
3
votes
3answers
525 views
How to use NASS county level crop data to estimate crop acreage in hydrologic regions?
National Agriculture Statistics Service (NASS) provides county level crop (Corn, Soybean, Sorghum, etc) data. I want to calculate crop acres on each subwatershed from the county based data. What is ...
5
votes
4answers
2k views
How to calculate polygon length and width using open source GIS?
How can I calculate the length and with of polygons using open source tools?
By "polygon length" I mean the length of the longest line within the polygon (update: to be correct, I just need the ...
5
votes
3answers
782 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 ...
7
votes
2answers
1k views
How to calculate average slope in a grid?
This is actually a two part question:
Which methods are there to calculate average slope by unit (say km²) for a given area? Are there any special requirements on the data - like additional ...
1
vote
2answers
5k views
How to calculate Raster Area per Polygon?
In ArcMap, I have a raster file that contains 6 classes of landcover and a shapefile that is the census data (OA boundaries and their population).
I want the area of each class in each OA? For ...
7
votes
3answers
520 views
How to get a list of adjacent lots to a road in ArcMAP and PostGIS/QGIS?
In the following map, I have:
A line / road layer
A parcel / lot layer
The Task:
Find and count the list of lots adjacent to the road with their types (parcel_type is a field in the parcel ...
8
votes
3answers
1k views
How to emulate Google Maps driving directions using pgRouting?
Would like to emulate google maps' driving directions functionality but use pgRouting instead. google's data over the project area & scale is quite a bit off so we want to use our own transport ...
8
votes
4answers
1k views
How to represent bimodal attribute value distributions on a map
I'm looking for a visualisation method that enables me to represent bimodal or even multimodal attribute value distributions on line features.
A bimodal distribution has two different modes that ...
6
votes
3answers
940 views
Calculating Length of Linestrings in WGS84 in Miles
I have a few thousand LINESTRING features in a MySQL database. I'm trying to figure out the cumulative length of all the lines -- in miles. Using the GLength function I can retrieve the length in ...
13
votes
6answers
4k views
Nearest neighbor between a point layer and a line layer
I've asked this question several times on stackoverflow and irc between #qgis and #postgis and I also tried to code it or implement it my self in postgis with no real answer.
Using programming (most ...
5
votes
2answers
331 views
Disaggregating aggregate GIS data using remote sensing
I haven't really done much with remote sensing imagery. I have census data for an area, and a TIFF raster image of the area.
I'm sure this is possible, is there a simple way to disaggregate the ...
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