Tag Info

Hot answers tagged

25

If your write load (incoming data stream) can potentially grow without limit (if the success of your web project will cause the amount of writes to grow grow grow) then go with Mongo, because it will be very hard to architect your way around the write bottleneck in PostGIS/PostgreSQL once you grow beyond the capabilities of a single high-end server (which, ...


20

The radius measurements surely are subject to some error. I would expect the amount of error to be proportional to the radii themselves. Let us assume the measurements are otherwise unbiased. A reasonable solution then uses weighted nonlinear least squares fitting, with weights inversely proportional to the squared radii. This is standard stuff available ...


14

As @user890 says, this very much depends on how the data will be used. Mainly there are two ways you could access the data: By loading it all into memory in one go and then access/query the data in-memory. By querying for specific features, bounding boxes etc. Formats like GeoJSON and KML are best suited for cases when you want to load everything in one ...


13

I think the OGR Vector Format list identifies just about every open source format I have ever heard of, and many many more. Each of those formats has its own advantages/disadvantages, so its hard to say which is the 'best'. For mobile apps, I imagine file size will be one of the more important deciding factors. For mobile applications, I would think ...


12

Firstly, you should know that the accuracy of these services is, and always will be, low. MaxMind Geolite city is free. If it is not good enough, you can apparently upgrade to a more accurate paid-version. I can't speak for the quality of the paid version, as I have never used it. If you like your SQL, download the CSV version. Load it into your ...


11

I've been using PostGIS for a few years and only recently started to investigate how I could use MongoDB to deal with certain use-cases. I was dealing with point data that had sparse fields - like OSM data with a varying number of tags per record, and since MongoDB has no schema, it lends itself well to this. I loaded a sample of this data into an instance ...


10

The best accuracy is obtained with ellipsoidal models. In the interests of simplicity you want to avoid those when you have to code distances yourself. We pay a price: given that the earth's flattening is about 1/300, using a purely spherical model can potentially introduce a relative distance error of up to 1/300 for very long routes: about 3000 parts per ...


9

The location you can infer from IP isn't very reliable (i.e. it kinda works sometimes). If you want a reliable location, consider the geolocation API that is part of HTML5. Note, however, that not all web browsers support it (yet).


9

I'd recommend deciding first who your target audience is. Are you writing it for the GIS crowd detailing technical issues of QGIS development? Or are you more interested in sharing your developed technique with folks interested in bird/nesting research? Having decided on that, pick up set of clever keywords that define your topic and use Google Scholar or ...


7

I think you're going to have to hunt this down on a state-by-state basis. A good place to start is the state spatial data clearinghouses. Google "spatial data clearinghouse" and most states will show up. Unfortunately some states (like my home state) are years behind in things like GIS, so you may not find universal coverage. Have you seen the mashup at ...


7

Your solution works for small distances, but it won't work for larger ones. The easiest way to see why is to look at the following map (taken from here): It is is a world map in equirectangular projection - longitudes and latitudes are simply linearly projected into X and Y axes. Your math can be represented by the blue rectangle. However, the blue ...


6

Check perhaps these papers: RADAR: an in-building RF-based user location and tracking system WLAN location determination via clustering and probability distributions


6

you can use maptiler and upload the file structure in your SDcard. Then add a TMS layer and set the getURL parameter to a function that return an image from SDcard: var mapBounds = null; var mapMinZoom = 12; var mapMaxZoom = 16; var tmsoverlay = new OpenLayers.Layer.TMS( "TMS Overlay", "", { // url: '', serviceVersion: '.', layername: '.', type: ...


6

I had basically the same question as user506706. I just couldn't believe that the Vector layer was the only layer to handle touches...so if all else fails...read the code. In OpenLayers-2.11/OpenLayers/lib/Events.js I found: BROWSER_EVENTS: [ "mouseover", "mouseout", "mousedown", "mouseup", "mousemove", "click", "dblclick", "rightclick", ...


6

After googling a bit more, I found this paper, Using Wi-Fi for Navigating the Great Indoors. I suppose the algorithm that handles multiple fingerprints, plus compass and accelerometer is what caught Apple's eye. When a gadget using WiFiSLAM wants to know its location, it analyzes the signal strengths and unique IDs of all the Wi-Fi networks around ...


6

Probably because it uses pre-calculated routes. As an example of an open source routing app with pre-calculated routes, OSRM uses contraction hierarchies to create shortcuts: http://algo2.iti.kit.edu/routeplanning.php PgRouting just creates the relations between source and target with the pgr_network_topology function. ...


5

I believe the Esri app for iOS can consume regular mapping services. The caveat is that your map services must be shared on ArcGIS.com. You would then search for your map services via Esri's app. There's a .pdf on arcgis.com with more info: using map services with iOS Edit: Good discussion in Esri's iOS forum.


5

You can check GIS Mobile Comparison by OSgeo. This page is used to describe comparisons between GeoSpatial Mobile applications to help users select suitable applications for their requirements.


4

This is all just my opinion but here are my 2cents worth, but yes you are on the right track. It really depends on the asset type you are capturing for a start and what kind of information you are planning to collect, and how much time you have to train people etc. Generally I prefer the PDA route as it allows faster information processing and cuts the ...


4

It sounds like you don't know the signal locations very well, so you need first to estimate them and then, given those estimates, triangulate your position. If you want some accuracy and realism, consider adopting a likelihood model for the signal strengths, finding the maximum likelihood, and making a gridded map of the location probability computed from ...


4

We did a prototype application based on CouchDB and Openlayers on Android device which could get tiles directly from local CouchDB into browser without web-server. This could be done because CouchDB has a REST interface. We also wrote a short paper about it, maybe it will help you.


4

This is a known flaw in most Android 2.x browsers, they do not handle multi-touch events. I know that Opera Mobile for Android does handle multitouch, and thus pinch zoom, but none of the other browsers I've tested (stock, dolphin, firefox).. The best strategy is thus to nag on the browser vendors..


4

You can buy high resolution satellite images from DigitalGlobe or GeoEye. You are not limited to these two map providers. There are too many options outside of these. You can also try Google Earth Pro for exporting images and with your license you can use Google Earth Pro images and data for marketing purposes as long as this data is not sold to any third ...


4

Yeah, mobiles integrate 2 kinds of GPS, Cell Tower/ Wifi Assistance GPS and the Satellital GPS, both services are free of charge but if you want to display your position on a Map, you need a offline map database or an Internet Connection to get into google maps or another maps service. Regards!


4

OsmAnd " is a fully open OpenStreetMap-based navigation app for Android. " [This don't require that you use navigation] Hints for using offline map data: offline map data files that can be used with OsmAnd have *.obf as file extension. in latest versions of these map files all vector map data, POIs and address indexes for offline search are included. ...


4

OpenLayers.mobile.js - a mobile focused build --> Includes a subset of the OpenLayers library to serve common mobile web app use cases. This build provides access to OpenStreetMap, Bing, WMS, WFS and vector layers; touch optimized controls; geolocation; vector editing and interaction tools. The examples tagged mobile can use this build. so it ...


4

I've done exactly the same thing for the same purposes - creating GIS-based rock climbing guides using GPS points taken with a mobile phone. I collected my points using an iPhone and the iGIS app. What I liked about iGIS was its ability to read/write directly to shapefiles, so you can get your attribute schema all setup outside of the app. Screenshot of ...


3

From the developer perspective I have to say choose the OS and platform that you are used to. If you are a Java developer propose Android, .Net developer use WP7, iOS developer use IPhone. The time it takes to get you started in the platform that you are familiar with should be reason enough continue using the same developer tools. As far as I understand ...


3

Jamo, You're on the right track. The biggest advantage is in data integrity. The sooner you get it into electronic format that fewer opportunities to introduce errors. The other is consistency. If you have an application with restricted options you can be sure that you'll get consistent results. There's nothing worse than different people calling the ...



Only top voted, non community-wiki answers of a minimum length are eligible