Frequently asked questions
Q: What is CSV?
A: CSV is text file with comma separated values. Structure of the boundary file is one Latitude, Longitude coordinate per line in decimal format. Example:
If polyline has to be broken (for example because of island), empty line is inserted to separate polylines from each other.
Q: Are boundary lines updated?
A: Boundary lines are updated from time-to-time. Last big update was on 10/04/2016 when almost all boundary files (city and county) were replaced. Old version was extract from openstreetmap.org, new version is from census.gov shapefiles 2015 version. Some country border lines were drawn by us, due the changes, feedback we get over our contact page.
Q: What do you mean with "simplified by Ramer–Douglas–Peucker algorithm"?
A: Boundary files would be too big for easy use. Ramer–Douglas–Peucker algorithm is method where boundaries can be simplified (some coordinates rounded and merged if they are near each other). Lat-long coordinates are rounded approximately to 0.00005. More info
For webmasters (real web developers, not "wordpress webdesigners")
Few useful tips and scripts for web developers. These examples require minimal programming (PHP) and math knowledge.
Q: How can I draw boundary line on my page?
A1: To show boundary data on google map, here is a simple solution in PHP, we used on our pages too. : Download Example1 ZIP, 29 KB (exampledata.csv, example1.php). This example will draw Florida boundary lines on Google map.
A2: To draw boundary data on map image using PHP (server side): Download this example 2 ZIP, 117 KB ( wmap.png, exampledata.csv, example2.php). This example will draw Florida polygone on map png image.
Few examples, what can you do with boundary data from our site:
Create world political map in any resolution:
Calculate areal distance between any point and nearlest border line. Tip: You have to check distance for each line of polyline. Stackoverflow.com: Shortest distance between a point and a line segment. Don't forget, that you need distance in miles (or km) calculated from latitude longitude. 1km.net: Distance between two lat-long coordinates.
US county boundaries
Population density map of Florida. File names on boundaries.us are FIPS codes, so you can dowload population data from census.gov and create nice maps.
Calculate minimal distance between two places (as the crow flies), example Malibu and Beverly Hills:
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