Interpreting Hydrographic Features in Aerial Photographs

DarkAisling · #1 08-05-2009, 10:02 PM

Kind of a geeky topic here . . . especially as I'm a cartographer (Geomatics Engineering Technologist) and I do quite a bit of mapping from aerial imagery.

I was just looking at imagery in Google Earth of the Bow as it runs through Douglasdale in Calgary . . . I wanted to see if I could figure out exactly where Rapala caught that trout ("where the Bow splits").

What significant determinations can be made from aerial photographs as far as fishing is concerned? The deeper pools will be represented as darker colours, won't they? Looking here http://maps.google.ca/maps?q=calgary...h&z=17&iwloc=A (hope that link works), there is a really dark spot in the river. Can it be concluded that this could be a good place to check out?

WayneChristie · #2 08-05-2009, 10:06 PM

Quote:

Originally Posted by DarkAisling

Kind of a geeky topic here . . . especially as I'm a cartographer (Geomatics Engineering Technologist) and I do quite a bit of mapping from aerial imagery.

I was just looking at imagery in Google Earth of the Bow as it runs through Douglasdale in Calgary . . . I wanted to see if I could figure out exactly where Rapala caught that trout ("where the Bow splits").

What significant determinations can be made from aerial photographs as far as fishing is concerned? The deeper pools will be represented as darker colours, won't they? Looking here http://maps.google.ca/maps?q=calgary...h&z=17&iwloc=A (hope that link works), there is a really dark spot in the river. Can it be concluded that this could be a good place to check out?

now thats a mouthfull! I think a lot of it depends on the weather when the photo was taken, shadows, the amount of water flowing at the time, (levels) and more. Im looking in google earth right now at the lake Im catching my pike at, and from what I see the dark areas dont really match reality, I know for a fact the area off the shore is only 2 feet deep and the holes are much more, but it doesnt look like it on the map. Also a lot of those were taken quite a while ago, since the highway I live on isnt even on the map yet.

WayneChristie · #3 08-05-2009, 10:10 PM

but it is a good starting point anyways, Ive found lots of fishing spots on google.

DarkAisling · #4 08-05-2009, 10:15 PM

Quote:

Originally Posted by WayneChristie

now thats a mouthfull!

LOL . . . my mat leave is almost up. I need to get my brain working again: so I can keep my clients happy and keep my job!

Quote:

Originally Posted by WayneChristie

Im looking in google earth right now at the lake Im catching my pike at, and from what I see the dark areas dont really match reality, I know for a fact the area off the shore is only 2 feet deep and the holes are much more, but it doesnt look like it on the map. .

I wasn't expecting to read that. Curious. I don't really do any hydrographic mapping anymore, so I don't have any sonar datasets to compare to imagery. Maybe after I'm back to work I can ask people to send me some datasets from their fish finders to see if I can come up with any solid conclusions.

ChrisRenaud · #5 08-05-2009, 10:17 PM

Just get a bathymetric map of the area (if available) and that will tell you where the holes and possible "honey holes" are..

WayneChristie · #6 08-05-2009, 10:17 PM

looked at that link, the spot is a natural for a deeper hole in any case, on the outside of a curve. Plus its very well lit, so Id say in this case its an accurate depiction of the river bottom. A lot of the images from google were taken at different times of the day, so the lighting isnt always to the best advantage. fellow geek LOL

WayneChristie · #7 08-06-2009, 10:31 PM

I checked out my lake again today, after staring at google earth last night for hours. OK way too much time on my hands too LOL I think some of the problem in relating the aerial photos to the depth may be due to weed growth too, the shallow areas that look deep on my lake are covered in thick weeds right now, so maybe if that was the case when the photos were taken it would and could be deceiving.

DarkAisling · #8 08-06-2009, 10:40 PM

Cool! That could be really useful information. Wasn't someone just asking how to find weed beds that weren't visible on the surface?

WayneChristie · #9 08-06-2009, 10:42 PM

Quote:

Originally Posted by DarkAisling

Cool! That could be really useful information. Wasn't someone just asking how to find weed beds that weren't visible on the surface?

thats easy! just cast a spoon LOL

troutpirate · #10 08-07-2009, 04:28 PM

i use it all the time to check out lakes and rivers and as everyone knows some areas have more details than others. i like to use a body of water im familiar with as a refrence point when im checking something out. i can usually get a good idea on what to expect, if i have a good refrence point. google has been really helpful for JNP waters

espeacilly for those who choose to chase the whispers to the monsters in JNP

WayneChristie · #11 08-07-2009, 08:38 PM

I was looking today again, as I was fishing and the sun occasionally peeked out so I could see, and the bottom had 2 distinct types of colour, light sand and dark or black sand in the lake I was fishing. I think this would give two different impressions when perusing aerial photos, since both areas seemed to share water depth in at least a few spots. I was using my anchor rope to measure it roughly. (gently just didnt work for me)