Request for guidance on mapping data

Posted by rolfedh@gmail.com on March 15, 2007, 9:55 pm

I'd like to generate a colored 'heat map' of readings from a hand-held
sensor being moved around a room by a person.

I envisioned something like having two "measuring spools" (or ranging
instruments), separated by a known distance, measuring the distance to
the sensor.

If one knows the length all three sides of a triangle, how does one
get the x,y coordinates of the sensor?

Any recommendations on:
- Other cost-effective or easy (out of the box) methods for achieving
this result.
- Software for transforming a signal and x,y coordinates into a color
image.

Thanks,

Rolfe

Posted by Joe on March 16, 2007, 11:41 am

> If one knows the length all three sides of a triangle, how does one
> get the x,y coordinates of the sensor?

The location is the intersection of two circles drawn centered at each
beacon. There are actually two possible answers, but if you assume
your beacons are along a wall, one of the locations will be out of
bounds and can be discarded.

Google for; robot sonar beacon navigation

Joe Dunfee

Posted by Fulliautomatix on March 17, 2007, 7:35 am

rolfedh@gmail.com wrote:

> I'd like to generate a colored 'heat map' of readings from a hand-held
> sensor being moved around a room by a person.
>
> I envisioned something like having two "measuring spools" (or ranging
> instruments), separated by a known distance, measuring the distance to
> the sensor.

String pull encoders???

> If one knows the length all three sides of a triangle, how does one
> get the x,y coordinates of the sensor?

It is at the intersection of the two circles of radius "measured
distance" centred at the measuring device.

r1^2=x1^2+y1^2
r2^2=x2^2+y2^2

x1=x2, y1=y2
Anyway...I'll get back to that

Any recommendations on:

> - Other cost-effective or easy (out of the box) methods for achieving
> this result.

easy? nope

- Software for transforming a signal and x,y coordinates into a color

> image.

Matlab
a VB script
Excel

look up RGB format - I think it is fairly easy to make an image from
data arranged in the right fashion.

Posted by Fulliautomatix on March 17, 2007, 8:00 am

Fulliautomatix wrote:

> r1^2=x1^2+y1^2
> r2^2=x2^2+y2^2
>
> x1=x2, y1=y2
> Anyway...I'll get back to that

http://www.sonoma.edu/users/w/wilsonst/Papers/Geometry/circles/default.html

Theorem 3.13, bottom of page,

d is the distance between the centres...you already know that - the
distance between the measuring devices

r1 & r2 are the measured distances from measuring devices to thermometer

x1 & y1, x2 & y2 are the coordinates of the measuring devices

x & y are the co-ordinates of the thermometer

x1y1 x2y2

0,0|-----.--------.-->y+

| \ /
| \ /
| r1\ /r2
| \ /
| xy
|
|
x+

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