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49
votes
11answers
103k views

Obtaining up-to-date list of US ZIP Codes with Latitude and Longitude Geocodes? [closed]

NOTE: This began as a question on Stack Overflow, which has subsequently been closed. I also noticed a similar question about Most Up-To-Date Source for US Zip Code Boundaries, but I believe this ...
48
votes
14answers
37k views

Converting ArcGIS Server JSON to GeoJSON?

I'm creating a web map using Leaflet, and I want to be able to grab feature layers from our ArcServer. I have successfully been able to retrieve a feature class as JSON, but Esri's JSON objects don't ...
48
votes
12answers
4k views

Geocoding USA addresses that cannot be sent over internet?

For a one-time project, I need to geocode a few thousand addresses. In the past I've used various online resources for this kind of thing (e.g., Google Maps API), but the addresses I'm working with ...
48
votes
4answers
37k views

Joining lots of small polygons to form larger polygon using PostGIS?

I have the following layer using SRID 27700 in postgis: It's every administrative region in the UK, and (as you can see from the colour grouping) each of them has a text field specifying the county ...
48
votes
8answers
25k views

Comparing QGIS and gvSIG? [closed]

Many debutant GIS users are asking me which one is better QGIS or gvSIG. Since I use Qgis and I don't have any experience in gvSIG, I aways say that both are very nice softwares and the chose is a ...
47
votes
2answers
51k views

Convert a pandas DataFrame to a GeoDataFrame

This seems like a simple enough question, but I can't figure out how to convert a pandas DataFrame to a GeoDataFrame for a spatial join. Here is an example of what my data looks like using df.head(): ...
47
votes
10answers
44k views

Alternatives to ArcGIS Online?

I am considering purchasing ArcGIS Online for a group of users who currently use about 5% of ArcGIS capabilities (ArcMap, simple map creation and information display) about 80% of the time. Primary ...
47
votes
7answers
140k views

What are Raster and Vector data in GIS and when to use?

What are raster and vector data in the GIS context? In general terms what applications, processes, or analysis are each suited for? (and not suited for!) Does anyone have some small, concise, ...
47
votes
3answers
59k views

Reprojecting vector layer in QGIS?

I have a series of layers of lines (shapefiles) in My Project. The CRS of some are different and to merge them they all must have same CRS. When I use Processing/Toolbox/Qgis_algorithims/...
47
votes
7answers
41k views

OpenLayers low resolution and/or shifts in QGIS print composer?

I'm having trouble with the OpenLayers Plugin of Qgis and the map composer: If I create an OSM-background layer and if I want to export this, the OSM-Layer looks perfectly all right in the normal ...
47
votes
7answers
11k views

Tuning PostGIS for production environments?

What PostGIS documentation have you come across that has been helpful when tuning PostGIS for a production environment? I would like to get together with my DBA to setup a Postgresql/PostGIS ...
47
votes
5answers
164k views

What is the maximum Theoretical accuracy of GPS?

I was talking with a potential client, and they requested that we plot some points with GPS, with a maximum (or should that be minimum?) accuracy of 2 m. This is an area with no WAAS, and I was under ...
47
votes
4answers
23k views

Free GIS workshops, tutorials, and applied learning material

This Q&A lists free as in $0 workshops in GIS and related fields that have their material available to view or download online. The list is not limited to FOSS GIS, as GISers usually use a ...
46
votes
7answers
93k views

Converting kmz file to kml?

Is there an easy way (like unzip) to convert a KMZ file to KML?
46
votes
6answers
251k views

Displaying local file in Google Maps?

How can I get a KML/KMZ file to display on Google Maps without a public facing web server?
46
votes
3answers
17k views

What is Lanczos resampling useful for in a spatial context?

GDAL includes a resampling method beyond the normal mix of nearest neighbor, bilinear, cubic and splines: "Lanczos windowed sinc resampling". I understand that its a convolution filter, but unlike ...
46
votes
5answers
19k views

Smoothing DEM using GRASS?

I have a SRTM DEM and I want to create a shaded relief from it. I created the shaded relief in GRASS and the result is very nice, but a little rough because the area is near flat and the DEM is 90m in ...
46
votes
1answer
26k views

Getting pixel value of GDAL raster under OGR point without NumPy?

I am working on a computational model of the abundance of wild pollinators across a landscape. The model itself is complete, and I am now struggling with a post-processing step. I have my GDAL ...
46
votes
2answers
12k views

Meaning of Simplify's tolerance parameter

The standard parameters of Douglas-Peucker's simplify algorithm are geometry and tolerance (e.g ST_Simplify in PostGIS). What's the meaning of the tolerance parameter? I know that the bigger the value,...
46
votes
3answers
11k views

Are there newer routing algorithms (than Dijkstra, A*) in GIS databases?

There are works like Reach for A* from Microsoft researchers and Highway Hierarchies by Sanders and Schtolz (if I spell the name correctly) from Karlsruhe Uni. Both of them reduce the calculations ...
45
votes
2answers
41k views

What's the difference between EPSG:4326 and EPSG:900913?

I am a bit confused on EPSG:4326 and EPSG:900913. I thought that they were both same. Though as I am placing my features over GMaps, which is EPSG:4326, I need to define the srsname of the WFS layer ...
45
votes
5answers
33k views

Bypassing 10 character limit of field name in shapefiles?

I'm exporting geometry with attached text attributes from oracle database to esri shapefile format (.shp) with Java and Geotools library. Attribute columns in our database have names with more than ...
45
votes
5answers
36k 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 "...
45
votes
13answers
25k views

Map matching links and ideas? [closed]

I'm using OpenStreetMap 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 ...
45
votes
1answer
60k views

How to install a QGIS plugin when offline?

Due to various IT policies at my workplace, QGIS is installed on a machine that is not connected to the internet. I wish to install a couple of QGIS plugins on this system. I have downloaded the ...
45
votes
3answers
66k views

Converting ArcGIS (*.mxd) file to QGIS (*.qgs) file?

I recently tried to use QGIS and I wondered if you can convert a draft ArcGIS map (*.mxd file) into a QGIS project (*.qgs file). This would avoid thematize the entire project.
44
votes
11answers
10k views

What is the most useful spatial R trick?

R is becoming pretty strong tool for handling and analyzing spatial data. I learned some useful things through questions like these at SO and thought it might be useful to have something simmilar, but ...
44
votes
16answers
73k views

Interview questions for hiring GIS Analyst?

What are some suitable interview questions to ask candidates for a GIS Analyst position? I am looking for techniques for interviewing analysts at varied experience levels (we are currently looking at ...
44
votes
8answers
54k views

Missing Processing Tools in Vector Menu of QGIS?

I'm missing all the usual processing tools in the Vector menu in QGIS 2.16 (eg vector overlay, analysis, etc). They do appear in the processing toolbox but there's no sign of them in the Vector menu. ...
44
votes
12answers
4k views

Seeking top tier conference in GIScience?

In many fields, such as computer sciences, it seems to be quite clear which conferences are top tier and how a paper accepted to those conferences compares to journal publications in the same field. ...
44
votes
3answers
46k views

Uninstalling QGIS that was installed using OSGeo

I installed QGIS using OSGEO4W, and would love to know how to uninstall it, because when I go to "Control Panel > Programs > Uninstall" the program does not appear in the list of installed programs. ...
44
votes
3answers
17k views

What is the current Web Mercator projection code?

The web mercator projection, popularised by Google Maps, seems to be given a new EPSG code every couple of years. EPSG:900913 (Google in calculator text) was an unofficial code EPSG:3785 - is the ...
43
votes
7answers
37k views

Choosing File Geodatabase (*.gdb), Personal Geodatabase (*.mdb) or shapefile format?

Previously, I have used geodatabases as an easy way to keep all files together rather than having dozens of shapefiles all over the place, and it is easier when finally exporting all the relevant data ...
43
votes
9answers
27k views

Open source methods for kriging?

I have a point dataset which I'd like to Krige, ideally using an open-source software package. If possible, I'd also like to choose the semi-variogram model during the process to improve the ...
43
votes
8answers
23k views

Downloading OpenStreetMap Data

Is there a straightforward way to download data from OpenStreetMap (OSM)? Using North America as an example, I realize Cloudmade (Cloudmade no longer provides downloads of OSM) and Geofabrik (http://...
43
votes
8answers
18k views

Select features that do NOT intersect in PostGIS

This seems to me like such a simple question (and it probably is) yet I cannot seem to find an example that gives me the answer. Using PostGIS, I just want to select points that fall outside of ...
43
votes
5answers
45k views

How to call gdal_translate from Python code?

Is it possible to use some gdal API to call gdal_translate from Python code? I do not mean simply executing the gdal_translate.exe from the file system, but rather call it somehow in code so I do not ...
43
votes
9answers
32k views

Tutorials to handle spatial data in R?

Does anyone know some good tutorials to handle spatial data in R? I know that there are some packages like rgdal and maptools but I haven't actually found usefull tutorials to get in touch with the ...
43
votes
3answers
51k views

How to calculate polygon centroids in R (for non-contiguous shapes)

I've spent a little while figuring out the answer to this question. It's not immediately obvious from a Google search, so thought it may useful to post the answer on here. There is also an additional ...
43
votes
2answers
31k views

What is the difference between EPSG:900913 and EPSG:3857?

I'm using the QGIS google layers plugin to digitize a parcel as a shapefile. Later I want to import it to PostGIS. I know that google maps use a special 'google mercator' projection. What is the ...
42
votes
18answers
25k views

Why do you use ArcGIS for Desktop?

I'm new to GIS, having only dabbled with ArcGIS for Desktop for about 4 weeks in 2007. The business I am at wants to target writing complete solutions that involve GIS as it would benefit their ...
42
votes
5answers
121k views

Showing popup on mouse-over, not on click using Leaflet?

Is it possible in Leaflet that popup opens on mouse-over, not on click? This is working for just one marker at a time, but I need it for a bigger number of markers: marker.on('mouseover', function(e)...
42
votes
12answers
8k views

Representing network flows? [closed]

For a project I'm working on, I need to represent network flows over 1,000 zones with directionality. Any suggestions on displaying the information in a nice and non overwhelming way? Any examples ...
42
votes
7answers
21k views

How to create svg symbols that have modifiable fill color, stroke color and stroke width?

I want to create some svg symbols for Qgis using Inkscape, those symbols must have attributes as described in the question. For the last two days, I have been experimenting as instructed by Sourcepole ...
42
votes
5answers
2k views

Generating equal sized polygons along line with PyQGIS?

I would like to create polygons along a line to use them for AtlasCreator in a next step. ArcMap has a tool called Strip Map Index Features. With this tool I can choose the height and width of my ...
42
votes
3answers
39k 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 floating-...
42
votes
4answers
33k views

Reading KML file into R?

I'm working with huge .kml files (up to 10 Gb) and need an efficient way to read them into R. Until now I've been converting them to shapefiles via QGIS and then back into R with readShapePoly and ...
41
votes
3answers
17k views

Reprojecting all geometries in PostGIS table?

I created a spatial table with SRID:4326. Now I want to change total projection to SRID:32644 into a new table. The old table should remain unchanged.
41
votes
12answers
34k views

Tablet or smart phone GPS vs “real” GPS

I've been reading a lot today about android and iphone devices being used for spatial data collection in the field and it sure seems to be that single purpose devices such as the extremely popular ...
41
votes
5answers
19k views

Calculating average width of 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,...

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