How do I take shapefiles and extract lat/lng coords so I can plot polygons on Google Maps?
http://www2.census.gov/cgi-bin/shapefiles/national-files
I asked this question here:
http://groups.google.com/group/Google-Maps-API/browse_thread/thread/18763b4b0cb996c7
and they told me WHAT to do, but not HOW to do it =P
Thx!
It depends on how you need to accomplish this. If you just need a few shapes, you can look up the coordinates in those files yourself. You can use those coordinates to create a GPolygon in Google Maps.
If you need lots of shapes - you'll need to do it programmatically. I would suggest using your favorite language to parse the XML file and retrieve the coordinates for each shape.
I had a similar problem last year when I was developing a screensaver to render presidential polling data. I didn't really want to invest the time to parse the Shapefiles data on the census site (The spec is here if you missed it).
Not sure if I actually saved any time here, but I ended writing a python app to render the 50 states onscreen, trace the edges and then store the data in a simple text format. Not sure if my data is high res enough for your application, but you can grab the data I generated here:
http://www.cannonade.net/pnt.zip
N.B. The data I generate are not latitude/longitudes, but with some scaling you should be able to translate them.
Good luck.
I had better luck using the ARC files at http://www.census.gov/geo/www/cob/index.html
I can't find the webpage right now, but I did find one that had actual code. Google something like "arc to kml" and go from there.
Related
I have two layers, first one is the ROAD layer and second one is the PARCEL layer as shown in Figure 1. I can get the data both in dxf and shp formats.
My task is to compute the area of intersection between ROAD and PARCEL layer, this is the easy part. I can compute intersection using QGIS or Geopandas easily. However, the difficult part is creating maps for each of the parcel. Sometimes, I have to create more then a hundred maps for each project. For mapping, there is a template that I have to use, which is similiar to Figure 2. Also, some attribute data should be included in the map, such as owner of the parcel.
These maps should be in both pdf and dxf format. Each map should be in A3 size. To be able to produce such maps, what libraries or programming languages should I use? I have experience in geopandas library but I am not sure if it is enough for this task.
Shoud I try QGIS plugin development or ArcPY? Could you please share your experiences and ideas about this problem?
I am looking forward to hearing from you,
Any help and suggestion is appreciated.
Thanks in advance
I'm interested in implementing some data visualizations as map layers. But I'm interested in generating data layers only above land area (land cover). A good example would be to plot population density over a coastal city. What is a good approach for this, when it comes to the data source and how to actually display layers with such detailed boundaries?
Technically, so far I'm using Leaflet.js and tiles based on OpenStreetMaps, but the question is not necessary technology specific. Also, I'm not interested in plotting this for the whole planet, but for areas of a few hundreds square kilometers (for e.g. a coastal city).
To better give an idea of what I'm interested in, this Koordinates map is something that is similar to what I'm interested in. However, I need something a bit more detailed on the borders.
Usually you need a desktop or server based GIS such coverage, but not JS to do the processing on the client side.
How you do the mapping (here: linking statistical data and land areas) depends on your data itself. You can load OSM based shape files into QGIS and do some python scripting or using the PostGIS commands to link your data and choose a map style.
Another idea would be http://geocommons.com that allow easy visualization if you upload CSV files.
Depending on your area of interest, you can obtain some highly detailed shapefiles from numerous sources. Especially if the local area provides GIS data to the public (many larger coastal cities do, e.g. New York, London). From there, you can create a GeoJSON text of the geometries (here's a free tool for that). Parsing the JSON is very simple and it's very easy to add it to leaflet maps. You can even get creative and add more keys to each geometry object with the data you want to visualize.
Hi there does anyone know a way, programatically or using a tool,
that I could create say a course around a Country and convert it into a series of GPS coords?
What I want to do is create a track then using the state of some unrelated data, lets say 0-100% completion, map that progression as a representation on the map.
I.E if the data is 30% completed, then represent a little running man icon on the map having walked 30% of it.
any ideas anyone? Thanks!
You can create a track in google earth and save it as KML. KML is a DSL that most geographic viewers understand. Once you have the KML, mining this data is a different story and theres no real rule to follow. You could parse directly the kml using a XML parser and get fun with your school math and vectors or you could download a KML parser library to get quicker results.
I am working on creating a tool to select a place via Google Maps API. This part is simple and I have no problems with it, but it is too specific. I want to do something similar to this, but need to accommodate the entire world, not just zip codes.
I would think the same effect should be able to be achieved by the highlighting an administrative level. Does this require KML file, and if so can anyone through a provider that might have this level of detail?
You can get administrative boundaries for the world here http://www.gadm.org/ or here http://www.unsalb.org/. You will not be able to achieve this with a single KML file though, as this would be one big file (I am talking about at least four hundred MB and there is a 4MB limit for KML files on Maps).
You will need to store the data in the db and pull out only relevant boundaries and draw them as polygons on the map. In other words it sounds like you might need a GIS server(open or ArcGis). Although you could build it from scratch using any geo-enabled db such as mySQL or MSSQL.
I have a json file thats roughly 480mb of geolocation points. I was wondering if someone knows of a good 'pattern' to use when trying to visualise the data. The problem I'm encountering is that the data has to be loaded into Google maps from the get go. This is causing all kinds of obvious issues.
I don't have to do this through google. It just seemed like the obvious choice.
With that much data, it may make more sense to handle it on the server side instead of client side. You could set up Geoserver with your appropriate data points. Using OpenLayers, you could overlay your points from Geoserver on top of Google Maps or potentially even on top of your own map if you want to cut out Google Maps all together. The heavy duty processing then happens on the server and only images are displayed in the browser. This cuts down on network traffic and the amount of processing the browser has to do. If you set up Geoserver to do caching, the server won't even have to work very hard.
It really depends on what kind of data this is.
If these are points for polylines or polygons you might try to encode the points (http://code.google.com/apis/maps/documentation/utilities/polylinealgorithm.html and http://code.google.com/apis/maps/documentation/utilities/polylineutility.html). There are also functions which you can use to encode the points. This will significantly reduce the size of your data.
You might also want to consider loading data depending on zoom level on the map. (I am not sure what you mean by "data has to be loaded from the get go" - you can load the data into the map depending on events, etc...) .
Fusion tables mentioned above will only accept 100MB of data.
I can be more specific if you explain the nature of your data and what you trying to do in more details. Hope this helps.
Try Google Fusion Tables