Stack Exchange Network

Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

Hot answers tagged

36

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, ...


29

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 ...


21

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 ...


18

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 go....


14

I think the OGR Vector Format list (link updated) 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 ...


12

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 ...


11

A new format that has come about recently is the Geopackage. This specification is built on top of the SQLite database, so it has the same single-file basis, but with the added benefit of being an OGC standard. As to file size, it is likely that the storage format is more compact than the .shp and .dbf format for spatial and attribute data used in the ...


9

Update 5/24/2016 Google's Project Tango has "Area Learning". Google Maps just announced that they are now "mapping the indoors". From Wired.com: "Google Maps 6.0 for Android launched Tuesday with a bold initiative: indoor mapping. Partnering at launch with a selection of businesses and public service structures, the new mobile Maps version allows ...


9

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: '...


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 ...


8

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 diagonal ...


7

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. http://workshop.pgrouting.org/...


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

There are a lot of options for collecting GPS point information on Android; I'm experimenting with several of them but none work terribly well - my use case is a bit tough, though, as I'm working out of low-flying Cessna aircraft and need constant GPS positions and to be able to instantly record a correct GPS position together with a note. OpenDataKit: ...


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 it....


6

If the area is known and stationary, why not skip GPS altogether and use beacons? You can get accuracy up to a few inches using that approach. As of today, there are many software+hardware SDKs that are coming out that enable you to pinpoint location using fixed beacons and a local coordinate system (which then you can translate to a different coordinate ...


5

Correct, the mousedown events do not occur on mobile with Touch events. Instead, you should use a Vector layer -- the Vector layers appropriately handle 'taps' and interpret them as select events.


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.


5

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 ...


5

Disclaimer: I am the founder of AmigoCloud. Sorry if it seems like shameless self-promotion. The idea is simple: If you have any popular geospatial format (ESRI Shapefile, FileGDB, KML, Spatialite, CSV, etc) you can use AmigoCloud to replicate that data as vectors (points/lines/polygons), to any standard iPhone/iPad/Android device. You can style and work ...


4

I am currently conducting research that attempts to implement Gaussian Processes for Signal Strength-Based Location Estimation in a distributed grid environment using parallelized algorithms of GPs that will be consumed on an Android application. While I do not have a working implementation yet, I will certainly keep those interested updated. And you are of ...


4

This question has been converted to Community Wiki and wiki locked because it is an example of a question that seeks a list of answers and appears to be popular enough to protect it from closure. It should be treated as a special case and should not be viewed as the type of question that is encouraged on this, or any Stack Exchange site, but if ...


4

Agree with Lennert, choose the right format for the job. However I have found Spatialite to be a pretty versatile format. You have the single file giving you have the flexibility in storing and sharing data like a shapefile, but you negate the issues you mention with character limits; whilst giving you opportunity to exploit the benefits of a spatial ...


4

There are a lot of different formats and the best depends on your data set you have, the tools you use and the things you want to do with it. Some of the ones I use: File Geodatabase & spatialite databases: A catchall that I like to use. It can hold all sorts of data and have relationships, indexing... I use gdb when working in an Esri environment, ...


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 Satellite 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.


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. you ...


4

GPS Essentials (11k+ downloads 4.4 stars) Exports KML or GPX - import to QGIS/Mapinfo "The Swiss army knife of GPS navigation! The most complete GPS tool on market: Navigate, manage waypoints, tracks, routes, build your own dashboard from 45 widgets. Dashboard Shows navigation values such as: Accuracy, Altitude, Speed, Battery, Bearing, ...


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