55
votes
16answers
8k views

How to Start Web Mapping?

I want to start working on a web map at work to map some of our statistics by city. I have an idea, but I'm not exactly sure where to start. Are there any definitive resources that provide step ...
68
votes
5answers
11k views

Accessing ArcObjects from Python?

I would like to be able to script some things that are not exposed via arcgisscripting or ArcPy. How do I access ArcObjects from Python? I'm working with ArcGIS Desktop 9.3.1 right now, but will be ...
54
votes
3answers
29k views

File Geodatabase (*.gdb) support in QGIS?

Following questions: Open Source Tool capable of reading Esri File Geodatabase (.gdb)? How to access file geodatabase in Qgis? How to get FGDB support in GDAL 1.9 without compiling? I have spent ...
20
votes
4answers
14k views

Layers with same coordinate system should align/overlap but do not?

I put 4 different layers into my ArcMap document, but only one of them will show up on the map! I should be seeing the other 3 layers as well. When I do a Zoom to layer, I can see one layer, but I ...
7
votes
4answers
6k views

How to fix QGIS error “Entry Point could not be located”?

Today, after returning from vacations, I started my QGIS 1.7 and got this terrible message: Help, anyone?
154
votes
48answers
36k views

What Makes a Map Beautiful?

Often times when we make maps it is based on our subjective interpretation of what is aesthetically pleasing. I would like if people posted examples of beautiful maps, displaying any phenomena in any ...
75
votes
4answers
45k views

How to measure the accuracy of latitude and longitude?

I am very new to GPS stuff. Suppose I have latitude and longitude as 19.0649070739746 and 73.1308670043945 respectively. In this case both coordinates are 13 decimal places long, but sometimes I also ...
29
votes
10answers
8k views

Identifying Coordinate System of Shapefile when Unknown?

I have a Shapefile but its coordinate system is Unknown, and there is no *.prj file. How I can identify it now? Are there any tools that could help?
11
votes
5answers
9k views

Calculating Lat/Lng X miles from point

I am wanting to find a latitude and longitude point given a bearing, a distance, and a starting latitude and longitude. This appears to be the opposite of this question (Distance between lat/long ...
27
votes
4answers
3k views

Performance of ArcGISScripting and large spatial data sets

I am currently writing a python script using the arcgisscripting module to process a reasonably large data set (~10,000 records in total) normalised over a small number of tables, 8 in total. The ...
7
votes
3answers
4k views

How to include variable in where clause of arcpy.Select_analysis?

I am trying to loop through a shapefile, selecting each feature in turn and copying it to a temporary shapefile to by included in a union analysis. I'm using a cursor to find the ID name for each ...
17
votes
6answers
7k views

Shapefile PRJ to PostGIS SRID lookup table?

I was wondering if there is such a thing as an shapefile PRJ to PostGIS SRID lookup table? Something that can translate the most standard shapefile PRJ definitions into the likely SRID. When using ...
117
votes
16answers
42k views

How do various JavaScript mapping libraries compare?

I am working on a web-based mapping system and I'm trying to figure out the best/most appropriate library to use. There are a few of them about and they each have pros and cons. Even after trying a ...
125
votes
12answers
28k views
10
votes
3answers
15k views

Converting ArcGIS layer style to Styled Layer Descriptor (SLD) file?

I am putting together a GIS server using GeoServer and need some help with importing my layer styles from ArcGIS 10 to SLD format. I have one layer in ArcMap properly symbolized and labeled, how ...
6
votes
3answers
5k views

How to use SRTM Global DEM for Slope calculation?

I have downloaded SRTM GDEM (~90 km resolution). I am using ArcGIS 10. I have tried to use spatial analyst to compute for slope. However, I can not compute for the slope. The output values has only ...
52
votes
5answers
19k views

How to build effective heat-maps?

Using ArcGIS, QuantumGIS, Grass, and/or GVSIG What are some of the tools and processes involved in building effective heat maps? What are the plugins involved? What are the major data requirements? ...
42
votes
7answers
3k views

What strategies, criteria, or rules to use for selecting coordinate systems?

What strategies, criteria, or rules do you use for selecting coordinate systems for (a) storing, (b) analyzing, and (c) displaying GIS data? (I humbly offer my reply to a related question ...
28
votes
3answers
30k views

Algorithm for offsetting a latitude/longitude by some amount of meters

I'm looking for an algorithm which when given a latitude and longitude pair and a vector translation in meters in Cartesian coordinates (x,y) would give me a new coordinate. Sort of like a reverse ...
36
votes
10answers
22k views

How to install GDAL with Python on windows?

Can anyone please explain to me in step by step instructions how to install GDAL/OGR with Python on Windows. I have Windows Vista and I have tried following the information on the website and it does ...
21
votes
3answers
10k views

Why is law of cosines more preferable than haversine when calculating distance between two latitude-longitude points?

In fact, when Sinnott published the haversine formula, computational precision was limited. Nowadays, JavaScript (and most modern computers & languages) use IEEE 754 64-bit ...
73
votes
34answers
4k views

What books, journals, and electronic resources are most valuable for expanding knowledge of GIS?

What books, journals, and/or electronic resources have you found most valuable for expanding your knowledge in the GI field? To which of them you come back most often? One item per post please, and ...
58
votes
15answers
19k views

What are Definition, Algorithms and Practical Solutions for Concave Hull?

Convex Hull A convex hull of a shape is defined as: In mathematics, the convex hull or convex envelope for a set of points X in a real vector space V is the minimal convex set containing X ...
23
votes
10answers
3k views

What are the existing solutions to automate generalisation/simplification of geographical data?

I am looking for existing solutions (softwares, libraries, methods, etc.) to automate the generalisation/simplification of geographical data as presented there, and also there. How do you proceed ...
16
votes
5answers
19k views

Get list of coordinates for points in a layer?

I've got a layer in QGIS that is comprised of points. Its attribute table doesn't have (show) the corresponding x and y coordinates for each point. Is there a way for me to extract a list of ...
37
votes
5answers
7k views

Why is the 'straight line' path across continent so curved?

This is the result of mapping the straight line path from a point in US to Poland using Distance Measurement Tool. Also, planes from Asia to US would travel almost over North Pole. Why is the path ...
24
votes
2answers
2k views

How accurate is approximating the Earth as a sphere?

What level of error do I encounter when approximating the earth as a sphere? Specifically, when dealing with the location of points and, for example, the great circle distances between them. Are ...
4
votes
4answers
984 views

How to Digitize Free Satellite Imagery in QGIS - Alignment issues with Openlayers Plugin

I am trying to digitize OpenLayers data (such as Google satellite imagery) with no success. Whenever I try to move or zoom the canvas the vector layer I digitized loses the position relative to the ...
25
votes
9answers
4k views

What are some resources for learning ArcPy?

I would like to learn ArcPy, but I do not know quite where to begin. Does anyone have any good advice on where I should start to learn ArcPy?
64
votes
14answers
14k views

What Makes a Map be classed as Badly Designed?

A poorly designed map can not only look visually unappealing, but can convey the wrong message, which could lead to bad decisions being made. I would like to ask people to post examples (that are in ...
24
votes
4answers
6k views

What raster smoothing/generalization tools are available?

I have a DEM that I would like to smooth or generalize to remove topographic extremes (chop off peaks and fill-in valleys). Ideally, I would also like to have control over the radius or level of ...
21
votes
4answers
3k views

Bulk load multiple shapefiles into PostGIS

I've got over a hundred data layers in shapefile format that I want to upload into a PostGIS database. They are all in the same projection, but represent different data layers so they do not have the ...
20
votes
1answer
2k views

How to create an accurate Tissot Indicatrix?

A Tissot Indicatrix is useful method for communicating at a glance the kinds of distortion a given projection is prone to (in the figure below, each of the red circles occupies the same area). I've ...
128
votes
56answers
10k views

What free programs should every GIS user have installed?

Note: This question is specifically about installed, desktop software. There is another question specifically about free cloud-based software and services. I'm not necessarily referring to ESRI ...
52
votes
7answers
4k views

What are some best practices for managing large amounts of geospatial data?

How do you manage your geospatial data? I have terabytes of data spread out over hundreds of datasets, and have an ad-hoc solution using symbolic links within projects which link back to an ...
23
votes
10answers
4k views

Alternatives to pgRouting

I was wondering if there are any alternatives to pgRouting tools. Thinking about it for a bit, I think the only alternative is to use R or RPY to do the analysis. Basically I'm trying to solve ...
25
votes
2answers
5k views

How to create a regular polygon grid in PostGIS?

How to create, on the shape of a polygon, a regular grid of polygons/squares of an given size, in postgis? I have thought about a function like Create regular point grid in Postgis only for squares, ...
22
votes
5answers
9k 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 ...
21
votes
5answers
10k views

What is difference between map layer and spatial dataset (e.g. feature class, shapefile)?

This may be very trivial question. To me they seems very similar in concept. What is the difference between feature class and feature layer?
9
votes
4answers
9k views

How to change a CSV layer attribute value from text to number?

I read in a CSV file for linking to a .shp file. All the variables that are just numbers came in as text. How do I change the text variables to numeric in QGIS?
7
votes
5answers
7k views

How to join multiple records to single feature?

apologies for what I'm guessing is a really easy problem to solve. GIS user, not programmer here. I'm trying to create a join/relate in QGIS where I have a shapefile of buildings and to that I would ...
57
votes
17answers
42k views

List of GIS applications for Android Tablets

I know that ArcGIS will someday be available for Android, but does anyone know of any other GIS apps that are available for Android tablets?
40
votes
13answers
6k views

Where can I find QGIS tutorials and resources?

After several recommendations, I thought I'd familiarize myself with the capabilities of QGIS. I downloaded the program, but apart from basic loading of data, I got lost (the help file wasn't much ...
9
votes
2answers
5k views

How to add Direction and Distance to attribute table?

anyone who can help. i just want to add direction (Bearing: i.e N 25 35 E) and Distance (Length: 125 meters) as my new field in polyline/line data. is there a plug-in to generate these fields? i tried ...
20
votes
12answers
5k views

Different approaches for map matching : links / ideas?

I'm using Open Street Map and its vectorial road network and I'd like to implement a map matcher algorithm. Currently I'm able, for each GPS position, to retrieve the nearest road segment and ...
23
votes
10answers
37k views

How to convert MapInfo TAB and/or MIF to SHP using free tools or ArcGIS for Desktop core product?

How do I convert MapInfo TAB and/or MIF files to SHP using only free tools or ArcGIS itself? I've not had much luck trying to do this in the past and I don't want to have to shell out for the ArcGIS ...
18
votes
12answers
12k views

Shapefiles to Text

How can I convert a shape file (GIS) to text? or, How can I extract the information in a shape file?
10
votes
4answers
18k views

How to add a simple WFS layer from GeoServer to OpenLayers map?

I'm trying to add one of the included datasets with GeoServer to an OpenLayers map. I've followed the OpenGeo tutorials, seen similar thread on here, but I can't seem to crack it. Can somebody take a ...
19
votes
1answer
1k views

What is most accurate coordinate system for calculating areas of polygons?

I have multiple polygons, all located offshore around the UK. I am trying to calculate the areas of these polygons in square kilometres, without splitting them by UTM zone. Is it possible to do this ...
5
votes
3answers
2k views

Python, comtypes and ArcObjects: Error creating AppROT object

I am experimenting with comtypes and ArcObjects under Python 2.6.5 and ArcGIS 10 SP1. I'm using the pure Python method to wrap the ArcObjects OLBs described in this answer, but getting an error in the ...

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