From the numbers to the pictures.
We took all the NMEA data from 10ths (feeled thousands) of test-drives and concatenated them into one big file, we then converted to the UTM/depth representation as mentioned in the previous episode.
This file was finally fed into a MatLab script, that produced a 3D image, where the depths are represented as colors, ranging from red to blue. Red was 0m and blue the maximum depth of this (shallow) lake with about -11m. MatLab does an automatic adaption of the colors and the axes in this case. In the first run, the x and y data (resp. Easting and Northing of UTM) were also plotted in blue color. The derivated picture looked like that.
This is not very spectacular, because the whole picture is covered with blue lines.
The next one is without them:
This Picture shows the color-of-depth-representation only, and the aspect ratio is now about to be correct. (sorry, these are only screenshots)
This "Pizza Margherita with blue Curacao"-like JPEG will later on be the overlay for the Google-Earth representation.
But first, a 3D view of the lake:
This view is from below, looking up, so the "deep-Spots" in the lake are better visible. The spikes on the right side are depth-artifacts, coming from the launch-point, where the sonar transducer hit the ground.
There are three "deep" holes in the lake, they go down to about -11m, but the rest is in 3-5m range covered with waterplants, which gives a "billowing" effect in the orange and red area.
I think this view can be improved by changing the color scheme and putting a grid over it. (some new project for Jochen...).
Now back to Google Earth.
In GE, there is an overlay feature, that lets you mix the GE view with a picture. Now we have a picture, but how putting it all together getting it matched in terms of size and aspect ratio?
First of all, i activated all tracks, that we have produced in the past (the GPS Vizualizer thingy - you remember?). This will give us a picture like that:
Then, we activate the Overlay function in GE and take the picture with the blue lines as overlay. After adjusting the transparency, we can see both pictures. And then we can tear,push,shove and move the picture until it matches the tracks. This overlay we keep. Then, we do the same with the other picture (The Pizza-view) and take the overlay, we created before as a reference. So we arrange an overlay over an overlay over an overlay. Quite strange, but it works. This last overlay is THE overlay. If we save it as a .KMZ (not .KML!!!). We can distribute it to anybody who wants a quick pizza-service on Google earth.
So it looks like, before the matching of the overlays:
This is the picture it looks like, when all is done.
I try to provide the .kmz file here as a reference. (i splitted up the picture and the depth legend, so the legend can be placed anywhere.
Back to reality:
We tried it out on the next weekend-dive we had in the lake. We took the course from the launch-point to the "big-hole" on the leftmost side from Google-earth (the ruler-function), adjusted our compasses to that course and we hit the hole exactly!
Theory and practice in perfect match - that´s rare.
This was the Past. On my first blogpost on this site, a member (Tom) gave me a link to a swedish company which provides a software that does all the above with a few mouseclicks and the 3D representation looks even better. I tried the demo in the last days and it looked good. I think i will spent the 99 Euro-bucks and try it out.
Is anybody out there who has eventually experience with that Software?
It is called DrDepth: http://www.drdepth.se/
This is not the end of the story...
I think there will be another episode. Maybe you remember the oscillations on the plots? The solution to that will be posted next.
Here is a sneak preview:
Fighting with the Integrator, the NMEA parser bug, and a new platform...
Bye bye fire-brigade ship have a nice stay on the cellar shelf with Ken.
Comments
Yes, you may be right. I also think, that a model-sized ship is not able to survive a longer journey on the sea.
Too high waves and the wind will make it impossible. Anyway, If you take the model with a bigger ship to the area of survey, and use the small ship as a robot, small "squares" of water may be surveyed (about 1k * 1km). The advantage of a robot-like ship is, that the straight-line behaviour is better than with a bigger (manually operated ship), assumimg friendly enivronmental conditions.
And the CO2-Emission figures will also be much better tham with a dinghy h:-)
The hull speed of the fire brigade-ship was indeed the problem. with about 1, length, i was close to the theoretical limit, which was about 5.5km/h.
Therefore (and for better stability), i built the Catamarane, which is described in the next Episode.
With that ship i also reached a "limit" at some 5.5km/h. Maybe, a better shaped hull will make it better.
Lake constance is already on the list :-), but i think there will be some legal issues cleared up first, before launching a UAV into this lake.
The crossing of the Lake between Überlingen and Wallhausen should be possible with no problems with the actual battery capacity and speed. Maybe one day...
Do you compensate for the longer path when the boat tilts and rolls and the sonar doesn't look straight down ? (I guess the emitted beam would be at an angle ? But maybe the echo sounder it is just a point source and depth is measured by the time of the first return signal ?)
When will you profile Lake Constance ? :-)
Thanks for the various hints regarding the vizualization software. I will have a closer look if business lets enough time in the next weeks.
The Software will surely be made available, but i have first to make some cleanups, that will it make better readable and/or adaptable to other users.
The marketing title should be "Google-Lake"
we can try to sell this name to the Google guys for tons of money!
The color scale should be right.
deep is blue is bottom
One thought: shouldn't the color scale by upside down, with deep at the bottom.