places on Earth are represented as places on usually flat surfaces, like print-outs or computer screens a method in the form of a mathematical equation for stretching and warping the lat/long grid of the globe to fit a planar map To avoid distortion, many projections are purpose-built: they are specific to an area, or are designed for functionality (e.g., measuring distances from a certain point). Web Mercator is the projection commonly used for web maps and typical web map-making software/tools/libraries. Local data in southwestern Pennsylvania is typically stored in PA State Plane (South) / EPSG 2272. It uses feet, not decimal degrees, and must be re-projected to use in a web map. It is the 'Wikipedia of maps': a publicy editable global base map that you can use in your mapping project. overviews Be A Mapper: How to contribute to OpenStreetMap Beginners Guide to OSM maptime: OpenStreetMap 101 some specific tasks To learn how to add any kind of thing to the map: / wiki / Map_Features Am I doing it the right way? / wiki / Good_practice The benefit of using a base map like OSM is that if you find a discrepancy, it is within your power to fix - and everyone wins. A spreadsheet saved as CSV file is a common way to store data. If it contains coordinates or addresses, it can be converted to a geodata. Head to the OpenPGH NDOCH GitHub page or the City of Pittsburgh GIS page to download some vector data to work with today. Most of these files are shapefile formant. To use on the web, you'll need to reproject them to Web Mercator and then convert them to either GeoJSON or KML. For converting and reprojecting, you'll need to use desktop Geographic Information Systems (GIS) software like QGIS (free) or ArcGIS (not free, but is the industry standard). First, a Very short introduction to QGIS. More detailed QGIS resources include QGIS 101 and a this comprehensive QGIS walk-through. supports creation, editing and conversion of geodata in common formats. It also has an API. You're in luck. You can take that spreadsheet of things you want to map and turn it into geodata through a process called Geocoding. Geocoding is the conversion of a human-readable location name (usually addresses) into a numeric location such as a latitude and longitude. The base element of this project is the basemap. To keep it simple, we are going to use MapStack. The image filters and effects offer a wide variety of customization. When you're happy with what you've created, copy the tile url of the live map by right clicking the map and follow your browser dialog to copy the link. Paste the url text from your MapStack map ino a text editor - we need to make some tweaks to get it ready for use in our map. We need to tweak this to make it generic and useful for Leaflet. The portions highlighted in red need to change. The bracketed pieces of the url example above -- {s},{z},{x}, and {y} -- are placeholders that allow for the correct tiles to be loaded by Leaflet into our web map. Leaflet is a JavasScript library that does the work of pulling our data and basemap together within HTML. Using the documentation from the starter tutorial on, we are going to start with the most basic components needed for a map: The result will be a web map that displays your MapStack basemap in the browser, with the ability to pan and zoom around. Leaflet displays GeoJSON data, but does not load an externally-stored GeoJSON file. You have a few options to load it, including using JQuery. Source.

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Last Modified: April 18, 2016 @ 10:03 pm