All Questions

3
votes
1answer
8k views

How to add GeoServer wfs layer on OpenLayers?

I can't seem to add a WFS layer like this. It works when i copy all this code locally but as soon as i change the values to point to my own layer within my own GeoServer this is the response viewed ...
33
votes
3answers
4k views

Openlayers Animation Examples and Algorithms

i wonder for a long time if people in this community uses openlayers for animation needs. we have know this that animating on browser is a little bit exhausting for it but when a map meets with ...
23
votes
5answers
3k views

Comparison of the different open source GIS servers

I currently know the following open source GIS servers: Geoserver: java based, vector and bitmap support, also supports. Is now on par with mapserver (performance-wise). mapserver: c/c++, used to be ...
30
votes
3answers
5k views

Spatial clustering with PostGIS

I'm looking for spatial clustering algorithm for using it within PostGIS-enabled database for point features. I'm going to write plpgsql function that takes distance between points within the same ...
29
votes
6answers
4k views

Downloading OpenStreetMap Data

Is there a straightforward way to download data from OpenStreetMap (OSM)? Using North America as an example, I realize Cloudmade (http://downloads.cloudmade.com/north_america) and geofabrik ...
17
votes
2answers
1k views

Acquiring ArcGIS-like speed in Postgis

I have been using Postgis 2.0 for 3/4 of a year now and while I really enjoy using it, excessive query processing time has rendered it basically unusable for my use case. I tend to do heavy ...
23
votes
18answers
17k views

Are there any free administrative boundaries available as shapefiles?

After learning about the US Census's TIGERLines datasets I'm addicted to GIS :) I've working with the following layers, from the USA data Country boundaries State boundaries County boundaries City ...
22
votes
9answers
1k views

Effectively displaying demographic data on a printed map

I would like to plot the following per zone (30 zones total) data on a printable/non interactive map: Average age Average household income Number of households Population density Number of people ...
12
votes
3answers
2k views

Converting SimpleGeo Places GeoJSON file to shapefile?

SimpleGeo has recently made their "Places" data set freely available which is GREAT, because now we can use it for our own purposes, even offline. So I went about downloading the 2GB dataset, which ...
16
votes
3answers
2k views

How can I calculate the average width of a polygon?

I'm interested in examining the average width of a polygon that represents the road surface. I also have the road centerline as a vector (which is sometimes not exactly in the center). In this example ...
12
votes
2answers
4k views

How to convert an .mxd file to a .qgs file?

I recently tried to use QuantumGIS and I wondered if you can turn in a draft format ESRI mxd loadable qgs. This would avoid thematize the entire project. Thanks for your help.
9
votes
1answer
3k views

How do I calculate the latitude and longitude of points using QGIS?

I'm trying to figure out how to calculate the lat/long of points using the QGIS field calculator. Is there an easy way to do this? I saw a previous related question, but it deals with a more advanced ...
22
votes
4answers
2k views

PostGIS: What are the pros and cons of geography and geometry types

My company uses geometry (the_geom) data type for storing geospatial data. I've recently been acquainted to the concept of geography (the_geog) data type which, as I understand it, stores the SRID ...
14
votes
9answers
3k views

Bulk Geocode 20 million records

Are there any free or reasonably priced databases for the US which can be searched and return latitude and longitude information?
12
votes
4answers
4k views

How to add an attribute field to an existing Shapefile via Python

I have a Python script that adds an attribute field to a Shapefile if doesn't exist. This is easy to do with ArcGIS (graphically or via Python), but I'm looking for something that doesn't depend on ...
9
votes
5answers
5k views

Is there an open source Geocoding tool which can be used commercially?

Is there any Geocoding tool which is open source and can be used in commercial application? We tried Google geocoding API's but cannot continue with it because of some licensing limitation. Now ...
22
votes
6answers
700 views

What tools for regionalization/redistricting can you recommend?

I am looking for tools for regionalization / districting in GIS. So far I have been able to identify Districting ArcGIS extension (now also online) REDCAP (currently limited to 50k input polygons) ...
19
votes
3answers
2k views

Most Up-To-Date Source for US Zip Code Boundaries

I was just wondering what the most up-to-date source for US Zip Code boundaries would be. My first thought was TIGER, whenever that comes out, but then I thought that the Postal Service might be a ...
16
votes
7answers
2k views

File Geodatabase Open API

Any ESRI boffins (insiders) know when this will be available? 2010, 2011? FINAL UPDATE now released 20th January 2011 - Can be downloaded here - ...
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 ...
10
votes
4answers
2k views

Simplifying polygons to linestring

I would like to simplify some polygons that represent rivers into linestrings. I assume that holes in polygons can be omitted. Anybody has some good idea how to simply do it? It would be nice, if it ...
7
votes
5answers
3k views

Comparison of Open Source Desktop GIS Packages

I'm curious as to what comparisons are out there between different Open Source Desktop GIS software packages. I'm aware that there has been a QGIS and gvSIG comparison on this site but I am looking ...
6
votes
4answers
1k views

How to create arcs between two points in Python?

I've been working on an python script automating the visualization of live point data. I have a table with two coordinate pairs. I'd like to connect these two point with an arc of a circle or similar ...
29
votes
3answers
4k views

LatLon or LonLat, what's the “right” way to display coordinates and inputs?

I'm trying to get a sense if this is an issue for others or every input/output should be labeled so user is not confused and just go with it? I think almost everyone pronounces it as "LatLon". Who ...
18
votes
9answers
2k views

Are there any Indoor GIS platforms?

What sort of infrastructure is needed to allow me to write a simple mobile app for indoor navigation? Professor Mike Goodchild said: the average American only spends 13 percent of the time ...
15
votes
4answers
3k views

Maximum number of point features in an OpenLayers vector layer

In your experience, how many point features can be added to an OpenLayers vector layer (new OpenLayers.Layer.Vector("Point Layer")) before it goes unusably slow? My use case is to display points from ...
14
votes
5answers
4k views

What's the difference between feature class and feature layer?

This may be very trivial question. To me they seems very similar in concept. What's the difference between feature class and feature layer?
14
votes
1answer
2k views

Calculating Flow Direction and Delineating Basins from Projected vs. Unprojected DEM Data

This is somewhat of a theoretical question stemming from some discussions with colleagues on the topic of implications with delineating basins with projected (e.g., Albers Equal Area) vs. unprojected ...
11
votes
7answers
3k views

Versioning with ArcSDE - Is it possible to cancel or reject edits once they've been posted?

I am using ArcGIS 9.3.1 and attempting to work with an SDE geodatabase (with one polygon feature class) that has already been registered as versioned. I'm new to versioning and am still trying to ...
7
votes
11answers
1k views

Logging GPS and Accelerometer Data - Device Suggestion?

I am looking for a device that can track my location (lat,long) and speed all day long. Perhaps, I need GPS and accelerometer data bundled together. What I want to do is to log my daily activities. I ...
40
votes
8answers
1k views

One dimensional map of the world?

Bit of a strange question but hope this is OK to ask here. Has anyone heard of a '1-dimensional' projection of the world map - that is mapping all the points on the globe to a single line? I was ...
16
votes
4answers
1k views

How to create regular point grid inside a polygon in Postgis?

How to create, inside a polygon, a regular grid of point spaced x,y in postgis? Like the example:
13
votes
5answers
495 views

How to make a GIS inventory?

My office will be seeing a big change in its GIS section. This section has been operational since the 1980's and has a huge collection of GIS data (i.e., shapefiles, raster files, data, etc) but never ...
12
votes
2answers
2k views

How can I switch baselayers as a user zooms in to the map in OpenLayers

I have a map which overlays Open Street Map data on imagery for Pennsylvania. As a baselayer to the roads (and eventually other layers) I have two baselayers - Blue Marble NG and USGS EROS 1ft ...
10
votes
6answers
3k views

ESRI ArcMap Add-in with app.settings not recognizing app.config changes

I have an ESRI Add-in developed for ArcMap which requires a configuration file. After spending a while trying to read config values from a single App.Config file (and always getting null) I believe ...
7
votes
4answers
1k views

How to reorder fields (permanently) in a file geodatabase

Using ArcGIS 10.0, is it possible to reorder the fields in a file geodatabase, and have the order persisted to the database? We considered exporting to XML, and writing a parser to change the field ...
15
votes
9answers
795 views

What's the value of being GISP certified?

Rephrased: I was wondering if someone could relate instances where being GISP certified helped : finding employment, getting promoted, drumming business up, noticed by your peers, the authority to ...
11
votes
4answers
8k views

How do you decide what interpolation method to use for resampling raster data?

The question pretty much says it all; are there hard and fast rules about which interpolation methods are suited to each kind of raster data? Any Golden rules, rules of thumb? Good books or articles ...
11
votes
5answers
3k views

How can I measure area from geographic coordinates?

If I have polygons in geographic coordinates (WGS84), how do I measure the total area each takes on the surface of the earth, taking into account the curvature of the earth?
8
votes
3answers
2k views

How to find the locations of the highest values in a raster?

Using ArcGIS 10, I have a raster where I would like to find the pixel with the maximum value in the raster and return its location (center of pixel) in decimal degrees. I would like to iterate through ...
8
votes
2answers
3k views

Selecting by bounding box with PostGIS

I have a large dataset in a PostGIS database. I am viewing it via a web interface that loads the data as GeoJSON. There is too much data to give the client all at once (10s of MBs worth...) so I would ...
8
votes
4answers
2k views

Code to calculate elevation profile along line from a DEM

Given a DEM (Digital Elevation Model) say in and a line (x1,y1) --> (x2,y2) (paired coordinates (x,y)), how can one calculate the elevation profile or cross-section projected on that line ? I am ...
7
votes
4answers
6k views

Overlaying lat/lon points on Google layer in OpenLayers

I'm stuck adding a vector point in lat/lon on top of a Google layer in OpenLayers. The point is moving when I pan the map. This doesn't happen if I replace the Google layer with a layer in WGS84. How ...
4
votes
2answers
3k views

“If then” VB Script code (or Python) equivalent to SQL's IN ('x','y',z') expression in ArcGIS Field Calculator question?

we need just like the following, only with multiple records selected... have tried the "xyz" in (1,2,3,4,5) SQL code but of course VB Script wants something else. dim f2 if [field1] = "foo" then f2 ...
10
votes
5answers
603 views

How to implement value-by-alpha map in GIS?

I've been doing some background reading about cartograms recently and stumbled upon interesting alternative - value-by-alpha maps. Concept is described in more details here and full paper is ...
9
votes
1answer
257 views

How to visualize azimuthal data with uncertainties?

I am trying to make a figure showing azimuthal data with a different range of uncertainties at each point. This oldschool figure from a 1991 paper captures the "bowtie plot" idea that I'm aiming for: ...
9
votes
11answers
3k views

DBF creation and manipulation without excel 2003

My company just upgraded to Office 2007 and now I am no longer able to easily manipulate and create dbf's. I do not understand MS's decision by removing this capability but alas there is no use ...
9
votes
3answers
4k views

How does ArcGIS compute the distance between two points with a non-equidistant projection?

This is a follow-up question to my previous one, Can you suggest some well-written introductory texts about coordinate system projections? Let's assume I'm working with the CH1903 map projection, ...
8
votes
2answers
650 views

How can I convert geomagnetic coordinates to geographic coordinates without doing the math myself?

I have some data which are in geomagnetic coordinates; that is, they are latitude and longitude, but in reference to the magnetic north pole in Canada rather than the geographic north pole. As you ...
8
votes
2answers
5k views

Change data source path in .LYR files in Arcgis 10

How can one change the source data paths for every layer file in folder X using arcpy? I've followed Updating and fixing data sources with arcpy.mapping as best I can, yet all I get is an unhelpful ...

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