opencage, 5 months ago

2/ Reverse geocoding is turning coordinates (latitude, longitude) into location info.

So 52.3877830, 9.7334394 becomes "Philipsbornstraße 2, 30165 Hanover, Germany" as you can see on our demo page.

https://opencagedata.com/demo

Those are the coordinates of OpenCage HQ, BTW

So far, so simple, right?

#geoeducation

opencage, 5 months ago

5/ Reverse geocoding may seems simple, but there are lots of things to consider.

First up, different parts of world are structured very differently, with different admin hierarchies and ways to show addresses.

We format the address as expected locally.

BTW - the templates we use to do it are open sourced: https://github.com/OpenCageData/address-formatting Pull requests gladly received!

#geoeducation

opencage, 5 months ago

7/ One small reverse geocoding pet peeve - people often send our geocoding API ultra precise coordinates. Like nanometer level.

There is no real need for more than 6 places past the decimal, see:

https://en.wikipedia.org/wiki/Decimal_degrees

#geoeducation

opencage, 10 months ago

12/ Obviously there are many, many more OpenStreetMap communities large and small all around the world than those we've had the chance to speak with so far.

Please get in touch if you'd like to share your local story on our blog 🙏🏾

We'd love to hear from you: https://opencagedata.com/contact

#OpenStreetMap #geoeducation

opencage, 10 months ago

2/ When you take a picture by default most digital cameras record all sort of meta info, and store that data in the resulting image file.

Things like type of camera, exposure time, etc.

This is known as "EXIF data". Exif stands for "Exchangeable image file format"

https://en.wikipedia.org/wiki/Exif

#geoeducation

opencage, 10 months ago

3/ Most photo editing software lets you see or write to the Exif data, for example you can fill in fields like copyright and name of the photographer

#geoeducation

opencage, 10 months ago

4/ There are also many sites online that let you see a photo’s Exif data. Here’s an example: https://jimpl.com

#geoeducation

Image uploaded and some of the Exif data is displayed

opencage, 10 months ago

5/ These days the most widely used cameras 📸 are mobile phones 📱 and phones generally know their location (from GPS, cell, wifi, etc).

Many phones record this location info in the exif data. We can extract and reverse geocode the location the photo was taken.

#geoeducation

opencage, 10 months ago

6/ How? Two steps:

1. get the coordinates from the exif data in the image

2. reverse geocode the coordinates into useful location information

Let's show a code example in javascript

#geoeducation

opencage, 10 months ago

8/ 🚨 note: an image might not have this data.

It may not have been recorded or might have been removed later. Newer operating systems make it easy to turn geolocation recording on and off, in general or for a specific photo

#geoeducation

opencage, 10 months ago

10/ Now we pass the decimal coordinates to our geocoding API and get the location 🙌

#geoeducation

opencage, 10 months ago

11/ 🚨 WAIT!!! 🚨

The precision of the Exif coordinates depends on the tech (GPS, cell, etc) used to capture the location. So they may not be perfectly precise.

But also showing a precise location might not be appropriate or have privacy implications.

See our guide on how to show less precise location like just the city or neighbourhood:

https://opencagedata.com/guides/how-to-preserve-privacy-by-showing-only-an-imprecise-location

#geoeducation

opencage, 10 months ago

12/ Precise geocoding might not make sense. Example: a tourist taking a picture right by the Eiffel Tower 🗼 in Paris 🇫🇷, probably wants their image geocoded as "Eiffel Tower" not the exact street address.

We offer this as a service to several large image processing customers.

#geoeducation

But the location is right by the Eiffel Tower
Location geocoded to "Eiffel Tower, Paris, France"