The process of extracting geographic, statistical, geometric, or scientific information from one or more related collections of GIS features and data.
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 ...
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
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 ...
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 ...
3
votes
0answers
174 views
How to estimate the average width of a sidewalk? [duplicate]
I have a table with two polygons representing urban block with and without the sidewalk: geomBlock and geomBlockWithSidewalk.
On my city we can approximate the polygons of geomBlockWithSidewalk to a ...
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 ...
3
votes
3answers
523 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 ...
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 ...
9
votes
4answers
507 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)
...
7
votes
2answers
281 views
How to create noise maps? (open source or scripted in ArcGIS)
In a previous role I helped create Noise Maps for Northern England.
The predicted noise levels was done using the IMMI package (which I can recommend) and the cartographic output was done in ArcMap. ...
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 ...
3
votes
1answer
359 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?
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, ...
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 ...
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 ...
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 ...
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 ...
8
votes
2answers
230 views
Finding polygons without right angles
Now we are digitizing some buildings in specified area. The obligatory rule for this work - in most cases buildings should have right angles. We are using QGIS with CAD tools for this work. But ...
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 ...
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, ...
3
votes
3answers
199 views
Summing attributes intersected by under a radius
Apologies - new user.
I am working with QGIS on Mac OS X and with shapefiles downloaded from the US Census Bureau that show population data by state and by county.
How do I:
select certain points ...
1
vote
0answers
148 views
mean coordinates in qGIS
I am using qGIS v 1.7.4 for MAC and trying to calculate mean coordinates for a set of points using ftools.
To calculate my result I am going to Vector -> Analysis tools -> mean coordinates and ...
0
votes
0answers
379 views
Sextane script error (os is not defined)
I want to build an analysis script using Sextante 1.0.9 on QGIS 1.8.0. I find an example script in Youtube. I tried this code but never worked always getting error. People say that Sextante is ...
