output (required) – the format of output (the options are xml, kml, csv or json).sensor (required) – true if the request is sent from a device with location sensor, otherwise false.key (required) – your API key (you can obtain it here).q (required) – the address to which you want get coordinates.We must send a request to with several parameteres. Geocoding Service provides way to get geographic coordinates via an HTTP request. The geocoding service may only be used in conjunction with displaying results on a Google map. For this purpose we will use Google Maps API and Geocoding Service (Geocoding is process of converting addresses into geographic coordinates). But not everybody realizes that I’ve heard stories of people trying to define boundary lines with Google Maps or Googel Earth, and it’s nowhere near accurate enough for that.Įven USGS DOQQ photos are 1-meter resolution, which is GIS-grade but not survey grade.This article contains code example of searching and saving GPS coordinates for an addresses stored in the database. Your point about Google Earth not being GIS or survey-quality is straight on. With satellite images, for most of the earth, it’s not even going to be that much of an issue, since the height of the satellite (around 300 miles) will be that much higher than most terrain it looks at, plus it’s usually looking down when it takes the pic. Not surprising, since the terrain is fairly flat here.Ĭorrection for terrain variation is a standard part of orthorectifying an aerial or satellite image, so I wouldn’t think that would make that much of a difference. If it were NAD27, it would have been *way* off (about 212 meters in my area).įrank – Tried turning the terrain off, and repeating the process. Xenonofarcticus – The DOQQ started out life in NAD83 UTM 12, and was re-projected with Global Mapper to WGS84 geographic coordinates. On a computer, the resolution is essentially limited to how far I can blow up the image, the pixel size, and how klutzy I am in positioning the cursor. That’s not the case for a digitized orthophoto, since the measurements are done by the computer. The stated error comes when you try to make measurements on a printed paper copy of the photo – your capability to mark a position on the map is limited by its size, and your ability to measure distances by hand. Note: If you have info about the Google Earth or Google Maps coordinate shift for your area, please post it in the comments section below (location and size of shift).Īnonymous: The doc you reference refers to published maps in paper format (check the date of the PDF spec). It wouldn’t surprise me if the magnitude and the direction of the shift varied from place to place if you’re hoping to use either Google Maps or Google Earth for determining positions with high accuracy, you should definitely do a ground check first to see what degree of coordinate shift there may be in your area. So you’ll get consistency if you export data from Google Maps “My Maps” to Google Earth, but the coordinates you get in the Google Maps KML file can still be off from the true values. ![]() That’s comparable in size and direction to what I saw in my previous post on Google Earth accuracy. With blue being the Google Maps point, and red the Google Earth point, you can see they’re displaced from the actual position by about 10 meters, or a bit more than 30 feet. So coordinates match up reasonably well between Google Earth and Google Maps.īut if I plot these points on top of a georeferenced USGS aerial photo: There’s a slight differential in the two, about 2.5 meters, but that’s almost certainly due to my inability to position the points exactly in the right location in both images, i.e. GM point is from Google Maps, GE Point from Google Earth. Next, I created a point at the same location in Google Maps “My Maps”:Įxporting the Google Maps point as a KML file, bringing it in to Google Earth, enlarging the view, and measuring the difference between the two: With the new Google Maps “My Maps” feature, I was curious as to whether you get any improvement in positional accuracy using Google Maps to create KML files for a point, rather than using Google Earth directly.įirst, I created a point in Google Earth at a highway intersection: The Google Earth coordinates corresponding to a feature on the earth can be off from the true coordinates of the feature, about 30 feet in my neck of the woods. I’ve posted before about absolute positional accuracy issues in Google Earth.
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