Poor mans navigation system.

[minor28]

Maybe this file can help. It converts the latitude and longitude to the corresponding point in pixel on the drawn map. The actual formula is calculated in "CalculateLatDistortion" function. Result is returned in "pScaleFactor".

Hope it helps. It works for me on every mapescale.

[dedndave]

low-level gain controls are rarely linear - it's probably anti-log - the opposite of what you want - lol
you can use an analog multiplier at higher levels - not really applicable, here
but, you need some info to make the tables

we wrote a routine to interpolate values from points in the table - bsl function as i recall
we were careful to write it so that it took roughly the same number of cycles, regardless of values
then, we added that time to the "current" time so when the answer popped out, it applied to "then"   :P

[KetilO]

Surprisingly, a field test shows that the gain level needed to detect bottom at different ranges is pretty linear.
Some of the levels are off probably due to bottom conditions like a steep slope.



Although I am nott really interested in depth abowe 100 meters since the main purpose of the sonar
is to detect shallow places and finding fish. It is still nice to know the depth on really deep places.

[KetilO]

Hi minor28

Yes, that helped a lot. Using the formula I only need the left,top and right,bottom points to convert lon,lat to pixel position and vica versa.

What confused me was the semi-mayor axis. It made me belive I could use it to get the height of the map in meters.
I now realise the formula can only be used to dtermine the relation between lattitude and y axis.

KetilO

[dedndave]

i really like the little fishies   :bg

[KetilO]

So you do.
What about this one. Its head is all about teeth and jaw.
Keep toes and fingers away, it will chop them off.

[dedndave]

he's an ugly critter - lol
bet he tastes good though

reminds me of the "goober fish" from starwars phantom menace   :P