Is there a way to convert "QRST-code" to longitude/latitude? - google-maps

Question

I did a lot of research for that topic - but it seems not enough, so I'm here asking for help :-)
Google Maps could use QRST-code for specifing a location. I've got a line like that:
trtqtqsss...
and so on. In some other forums I've found out that GM once used that in an URL-Syntax. But now it seems it doesn't work anymore - or at least I don't know how.
Here is an example of the link that won't work anymore:
kh0.google.com/kh?n=404&v=8&t=tq
kh1.google.com/kh?n=404&v=8&t=tr
In this URL, the quadrants are specified with the string after t=.
Is there a converter or something like that?
Thank you in advance!

Answer 1

Partial answer:
From what I gather, the long string of trtqtqss indicates, in essence, a binary search for the location. It roughly translates like this:
Start with the letter t. This gives you "the sholw world"
Look for your point on the map. If it's in the top left quadrant, add a q. If top right, add r. Bottom right, add s. Bottom left, add t.
Zoom in on the new quadrant. Repeat.
Every time you add a letter you halve the size of the tile, and find a new bottom left corner. If we think of the world map as a rectangle of width and height = 1, we can find a new corner for each character added. This is the essence of the algorithm you linked in your comment.
With that, plus the "Rosetta stone" (again from your link) of a known string-to-satellite image translation, I give you the following code. This will give you the Longitude/Latitude of a point based on your string. Compile it, then pass the string as argument to the executable:
#include <stdio.h>
#include <string.h>
#include <math.h>
double NormalToMercator(double y) {
double pi;
pi = 2 * asin(1);
y -= 0.5;
y *= 2 * pi;
y = exp( 2 * y );
y = ( y - 1 ) / ( y + 1 );
y = -asin( y );
return -y * 180 / pi;
}
int main(int argc, char* argv[]) {
double x=0, y=0, scale=1;
char buf[100]={' '};
int ii;
buf[0]=argv[1][0];
for(ii = 1; ii < strlen(argv[1]); ii++) {
buf[ii-1]=argv[1][ii];
scale *= 0.5;
switch (tolower(argv[1][ii])) {
case 'q':
y+=scale;
break;
case 'r':
y+=scale;
x+=scale;
break;
case 's':
x+=scale;
break;
case 't':
break;
default:
break;
}
printf("the string %s gets you to (x,y): %.9lf, %.9lf\n", \
buf, x, y);
}
printf("the final lat/long is %.5lf, %.5lf\n", 360.0 * (x - 0.5), NormalToMercator(y));
}
The intermediate printf statement is there to show you how the algorithm is slowly making its way to the right location. I tested this with the string from the link in your comment (tsrrtrsqsqqqrqrtsst), and got the coordinates 153.39935ºE 28.32372ºS (note - a negative number for longitude means "W", and a negative number for latitude means "S". I got 153.39935, -28.32372). When I entered those in Google maps, I got the picture of the hospital that you get when entering the link from blog post.