Puget Sound Bathymetry over Google Maps

lamont · Post by **lamont** » Sun May 20, 2007 10:23 pm

http://www.scriptkiddie.org/bath

I've been working on that for a couple of months now. There's a whole lot more features that I've been testing and are in the pipeline to release, but I need to figure out if I can serve the uderlying bathymetry data publically with my latest refactoring without creaming the heck out of my upstream bandwidth and my server CPU.

This is buggy and not even really a beta test. The two highest zooms don't have any tiles generated for them. The script that I've got now that generates the tiles I estimate takes 2 days to run and I needed to fix some bugs and run it again so I decided to just throw what I've got out there.

You'll notice that lake washington is 18.75 ft lower than it should be. I tried to fix this but transposed x and y coordinates and accidentally hit Dungeness Bay / Sequim with a 18.75 ft tsunami (or maybe its global warming?)...

The source of the underlying data is here:

http://www.ocean.washington.edu/data/pu ... m2005.html

Joshua Smith · Post by **Joshua Smith** » Sun May 20, 2007 11:09 pm

That looks reeeaaally interesting.....I'd like to see it when it's a bit more polished. I've been thinking about looking for a chart that shows the Sound like a USGS map shows elevations....those all seem to stop at sea level, for some strange reason. Nice work!

lamont · Post by **lamont** » Sun May 20, 2007 11:14 pm

how painful was the response time? i was watching you in my access logs and it seemed like it was a big laggy...

(i'll find out for myself tomorrow at work though...)

lamont · Post by **lamont** » Sun May 20, 2007 11:21 pm

one performance bug i just found was that if it accesses tiles outside of the bounding box it gets back a 404 which the browser never caches and will slow down page displays... there's a documented fix for this i'll be able to use to return blank.jpg file which should speed up initial page loads and reloads on zoomed out images...

Joshua Smith · Post by **Joshua Smith** » Mon May 21, 2007 6:04 am

lamont wrote:how painful was the response time? i was watching you in my access logs and it seemed like it was a big laggy...

(i'll find out for myself tomorrow at work though...)

Well, there was some lag before the overlay showed up, but not too bad.

nwscubamom · Post by **nwscubamom** » Mon May 21, 2007 8:27 am

This is TOO cool!!!

The response time for me was pretty good too! Not instantaneous, but mostly even faster than what I find for Google Earth when it's attempting to resolve.

I've been poking around Hood Canal - pretty cool, the Pinnacle shows up nicely there.

I'm impressed!!

- Janna

Tom Nic · Post by **Tom Nic** » Mon May 21, 2007 9:00 am

VERY nice Lamont! Way cool!

I've been poking around Day Island and Titlow... explains why heading into the shallows from the South part of Day Island Wall is such a long swim! The shallows are much "larger" to the South than the north.

Is there a depth gradient chart to go with the colors? Would the narrow yellow band indicate a wall? It looks like the same wall goes on up the Narrows to Titlow... interesting! I notice that the yellow band is wider across the narrows... so I'm assuming that any very narrow band would indicate a small area with that depth, so a wall of any "height" (depth in this case) would show up as a narrow band of color.

Very nice!

Seaslave · Post by **Seaslave** » Mon May 21, 2007 9:38 am

Very cool Lamont. I can't imagine the amount of time this must take to build. Do you have plans to extend the data up into the North San Juans, my neck of the woods? Either way, outstanding job, thank you.

Mathue

Joshua Smith · Post by **Joshua Smith** » Mon May 21, 2007 9:46 am

This thing is great! I've been playing around with it some more, looking at Cove 2 and Muk, Hood Canal- (The pinnacle does show up nicely) Really cool, Lamont!

lamont · Post by **lamont** » Mon May 21, 2007 10:03 am

Tom Nic wrote: Is there a depth gradient chart to go with the colors? Would the narrow yellow band indicate a wall?

i think the yellow tends to visually look narrower because it gets washed out by the colors on either side of it.

but in general it works like a contour map so the closer the contours are together the steeper the slope will be. big wide bands of color are going to be very flat (look at edmonds or alki pipeline)

lamont · Post by **lamont** » Mon May 21, 2007 10:09 am

Seaslave wrote:Very cool Lamont. I can't imagine the amount of time this must take to build. Do you have plans to extend the data up into the North San Juans, my neck of the woods? Either way, outstanding job, thank you.

Mathue

well, the data i pulled off that UW site which is 10m resolution. there's a previous 30m resolution DEM which covers more area which i could use to cover more area at lower resolution. there's also some nice 3m and 4m DEMs of elliott bay and commencement bay which i want to get as overlays on top of this data.

there's also the raw underlying NOAA bathymetry data, but it is all in ungridded X,Y,Z data soundings and not a DEM grid like this data -- and i've checked out some publically available geomapping tools and haven't found one with a good algorithm for taking data which is both highly under- and over- sampled in parts and turning it into a consistent grid.

i know that around the Al-ind-eska-Sea and the vertical barges that the underlying data is actually much better than the 10m grid so i could probably use a 3m grid over that section of the data -- but i'm not there yet.

wait until i get the NOAA wreck and obstruction database overlayed as waypoints on top of this stuff... i've got it all working, but its on the old mapserver engine and i just need to port it...

lamont · Post by **lamont** » Mon May 21, 2007 10:20 am

if anyone was wondering, here's the color values used for the default scheme which is on there now (ft, R, G, B):

0 0 0 0
-1 255 0 0
-66 255 255 0
-132 0 255 0
-198 0 255 255
-264 255 255 255
-330 255 0 255
-396 0 0 255
-967 0 0 1

so the middle of the green band is the limits of recreational diving.

nwscubamom · Post by **nwscubamom** » Mon May 21, 2007 10:26 am

Will we have the ability to overlay our own waypoints onto the map so we can see where dive sites are etc? Like on Google Earth?

- Janna

lamont · Post by **lamont** » Mon May 21, 2007 10:43 am

nwscubamom wrote:Will we have the ability to overlay our own waypoints onto the map so we can see where dive sites are etc? Like on Google Earth?

- Janna

I've been thinking about going all web-2.0 wikipedia on it and setting up waypoints and divesite reviews public/private, etc, but for now its static content... wikifiying it is probably at least 6 months out...

i just switched over to the new tile set, which has lake washington depth corrected for the lowest level of the lake rather than MLLW of the sound. it also has all but the final level of zoom generated (which took all night, it just started on the final level of zoom which will take another 1.5 days). and the tidal wave in dungeness bay should be gone...

looks like i need to fix I-5 at MLK way now though...

nwscubamom · Post by **nwscubamom** » Mon May 21, 2007 11:18 am

Well, no matter how you cut it, it's USEFUL and really neat!

Waypointable or not!

Nice work, keep at it!

- Janna

lundysd · Post by **lundysd** » Tue May 22, 2007 12:39 am

freakin cool

dsteding · Post by **dsteding** » Tue May 22, 2007 8:52 am

Really cool Lamont-

One bug I just noted. The bathymetry overlay is now covering the Google street base map as well as the water areas (it tiles over as white). It wasn't like that the other night, so I assume this is a result of you tweaking other things . . .

An awesome piece of work!

lamont · Post by **lamont** » Tue May 22, 2007 9:40 am

dsteding wrote: One bug I just noted. The bathymetry overlay is now covering the Google street base map as well as the water areas (it tiles over as white). It wasn't like that the other night, so I assume this is a result of you tweaking other things . . .

i think you've probably got a buggy browser that doesn't support transparent PNG correctly. IE6 and IE7beta are known to have these bugs. the latest IE7 or mozilla/firefox are known to be good (not sure about latest IE6). you were probably using a different browser the other night?

dsteding · Post by **dsteding** » Tue May 22, 2007 10:55 am

lamont wrote:
dsteding wrote: One bug I just noted. The bathymetry overlay is now covering the Google street base map as well as the water areas (it tiles over as white). It wasn't like that the other night, so I assume this is a result of you tweaking other things . . .
i think you've probably got a buggy browser that doesn't support transparent PNG correctly. IE6 and IE7beta are known to have these bugs. the latest IE7 or mozilla/firefox are known to be good (not sure about latest IE6). you were probably using a different browser the other night?

You are correct, last night it was firefox on my mac. Today it was IE6 at work . . . nice diagnosis.

lamont · Post by **lamont** » Tue May 22, 2007 11:15 am

dsteding wrote: You are correct, last night it was firefox on my mac. Today it was IE6 at work . . . nice diagnosis.

i need to setup a FAQ page since I'm reasonably certain you're only going to be the first person to ask that question...

it looks like its a little over halfway done with zoom 17 now, but it goes west-to-east so it barely gets to the west side of puget sound...

i think i've got an algorithm i can use to figure out which tiles are entirely transparent at higher zoom levels, verify there are no points in the area in the parent DEM and then autogenerate all the empty pngs for all the zooms down to 17 which should speed things up a lot... most of the 2 days it spends generating tiles is spent generating empty tiles at zoom 17...

Marc · Post by **Marc** » Tue May 22, 2007 11:17 am

I have to tell someone how much I hate Internet Exploder..... This week it is you guys. thank you.

dsteding · Post by **dsteding** » Tue May 22, 2007 11:29 am

Blitz wrote:I have to tell someone how much I hate Internet Exploder..... This week it is you guys. thank you.

And, I hate you because you are going to Oahu

yoda · Post by **yoda** » Tue May 22, 2007 11:51 am

wow Lamont...looks great on this end...and not a bad response time either! Good stuff - many thanks for the work you've put into it!

Marc · Post by **Marc** » Tue May 22, 2007 2:18 pm

dsteding wrote:
Blitz wrote:I have to tell someone how much I hate Internet Exploder..... This week it is you guys. thank you.
And, I hate you because you are going to Oahu

Less than 48 hours out.

....and I am going with a hot chick.

lamont · Post by **lamont** » Tue May 22, 2007 10:49 pm

just deployed some upgrades. supports url parameters for lat,lng,zoom has linkToMe which rewrites the url line to give a link to the current display, has entry box for lat/lng and when you click on the map it outputs lat/lng in a message box

Northwest Dive Club

Puget Sound Bathymetry over Google Maps

Puget Sound Bathymetry over Google Maps

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