There are two cases when the exact alignment feature is useful :
- In your app, you want to use a base map provider that is not available in IndoorAtlas Web tool.
- You have a geo-reference floor plan i.e. you already know pairs of (latitude, longitude : image coordinate x, image coordinate y).
Example: Finding Geo-reference Coordinates from Google Maps
Here's the example floor plan image we want to use. Now we need to find a geo-coordinate for 2 corners of the image.
In Google Maps, you can simply click the corner of the building to get it's geo-coordinate. Copy and paste the coordinates to your favorite notebook with in the format:
Using Image Corner Geo-reference Coordinates to Align Floor Plan
Next, go to app.indooratlas.com, open your venue, and click "Add floor plan" on the top bar.
After you have uploaded the image, you will see it on top of the world map. Now, click "Align using image corner geocoordinates".
Click on the coordinate field of the first corner you have copied the coordinates for. Then paste the coordinates (it fills both lat and lon). Do the same for the other chosen corner.
Then, click "Align floor plan".
Now you should see the floor plan aligned over the base world map. Note that the alignment does not fit perfectly, because base maps have slightly different aerial image camera angles etc.
In fact, this is the likely reason you are using this feature -- aligning the image so that it fits perfectly on one of the base maps that are not available in IndoorAtlas' app.indooratlas.com.
Finally, click "Save. Now, when your App receives the floor plan bounding box from IndoorAtlas SDK and you align the image on google maps, it should fit perfectly.
Similarly, if you use WGS84 geocoordinate positions from IndoorAtlas SDK and plot them on Google Maps, the coordinates should have no offset.
Using Any Geo-referenced Coordinates to Align Floor Plan
In case it's difficult to get geocoordinates for the image corner coordinates (quite typical case), you can identify some other easily recognizable points, e.g. building's corners -- assuming your floor plan image spans the building corner area.
To use those coordinates, you first have to save the image in some (rough) alignment, then go to "Edit floor plan alignment".
Similarly as in the Google Maps example, find the geocoordinates for 2 points on the image. Then create 2 lock points with the + button and move the lock points (blue marker) to those same positions on the image.
Next, copy-paste the geocoordinates to the corresponding fields and click Save. Now the image is aligned.