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 Post subject: Topo maps are unreliable when away from the travel routes
PostPosted: September 12th, 2008, 4:03 pm 
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Don't count on the topo maps being consistently reliable across the map, even though you know it depicts every little bay and rock shoal on your canoe route. I first found this out when trying to explore the land beyond the shores of the French River. On a recent trip into the Kawartha Park, we used a topo to try to reach a lake by bushwhacking, and were thoroughly thwarted by the terrain and the inadequate representation that the topo map gave.

Here's the topo map of the area. We tried to cross from Buzzard Lake at the left edge of the map to Elm Lake at the bottom. The topo 1:50,000 has a lot of the details, like wet expanses with open water just represented as "green" = forest.

Image

Google will reveal that there is a lot more water in reality, but the resolution is not good enough to make an accurate judgement of what's ahead.

Image

If you should have a GPS with built-in map with you, like the Garmin topomap, it would tell you just fine where in relationship to the large lakes and the elevation lines you are, but there is no hint of the wet obstructions that are ahead of you as you are trying to cross the land.

Image

Ontario has a crownland-use-Atlas which shows the best details. Note all these little bodies of water that are in the area - and you still don't know whether you can cross or have to do major detours... :wink:

Image

Here's a picture of what it looks like, standing on the ground and trying to figure out where to turn:

Image


So, here's the moral of the story: Do not trust the detail of your topo when away from the commonly trodden areas!


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 Post subject: Re: Topo maps are unreliable when away from the travel routes
PostPosted: September 12th, 2008, 4:35 pm 
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Is it really that you were off well travelled routes?
Or does the detail depend more on the water level at the time the aerial photographs were taken?
Or on the patience/attitude/whatever of the person who drew the map, in those days before computers?
Yours in paddling, Allan

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 Post subject: Re: Topo maps are unreliable when away from the travel routes
PostPosted: September 12th, 2008, 5:13 pm 
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I think generally topo maps are reliable but what is the date of the last field survey?

I had a similar episode in Wabakimi in 1991. Looking at the fine print on the map I was using, the last field survey was in 1953.

So :doh: of course the lake I was looking for was not a bog, not paddleable nor walkable.


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 Post subject: Re: Topo maps are unreliable when away from the travel routes
PostPosted: September 12th, 2008, 5:33 pm 
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Allan Jacobs wrote:
Is it really that you were off well travelled routes?
Or does the detail depend more on the water level at the time the aerial photographs were taken?
Or on the patience/attitude/whatever of the person who drew the map, in those days before computers?
Yours in paddling, Allan

Off the well-traveled route: the locals travel Long and Buzzard, with a portage leading to the south (off the map) and those lakes with their shores are accurately depicted. So is Pilot Lake and probably Elm as well.. Whoever goes hunting will enter the bush. From Buzzard, a trail of cairns started but petered out after a few hundred metres, and at some point we crossed a spot where an ATV seems to run a few times a year.

I assume that all those maps were drawn with whatever was available at that time - and that material got better over the years, of course. So, the water level probably makes little difference for the draftsman. I think the difference comes from the tremendous amount of work and interpretation needed to translate a landscape from aerial images to topo format. It's work, and time's money. Thus, I think the draftsmen are expected to focus on inhabited and commonly traveled areas and give it the expected detail. But I think they are given leeway to generalize in other areas in order to get the work done.


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 Post subject: Re: Topo maps are unreliable when away from the travel routes
PostPosted: September 12th, 2008, 5:38 pm 
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littleredcanoe wrote:
I think generally topo maps are reliable but what is the date of the last field survey?

I had a similar episode in Wabakimi in 1991. Looking at the fine print on the map I was using, the last field survey was in 1953.

So :doh: of course the lake I was looking for was not a bog, not paddleable nor walkable.


Yup, the land changes.

In the case above, the topo is dated 1983 and it seems to have anticipated the drying up of watercourses and ponds.... :wink:

But the OLUatlas has got it nearly right... I don't know the published date though (a real shortcoming of the internet, by the way).

Jest aside, I think the mappers just take shortcuts when they believe no one will care.


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 Post subject: Re: Topo maps are unreliable when away from the travel routes
PostPosted: September 12th, 2008, 5:47 pm 
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Actually I can think of some huge squishy spots in Wabakimi not defined as wetlands.

It did not help that there is little elevation change between lake and shore and the lake was supplying a lot of moisture to the adjacent 200 m. It was a very high water year.

One portage was actually under water.

Oh well thats why we explore by canoe.


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 Post subject: Re: Topo maps are unreliable when away from the travel routes
PostPosted: September 12th, 2008, 6:10 pm 
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Erhard, there's another set of maps available from the MNR - the Ontario Base Map series. 1:10,000 scale south of the French and 1:20000 north of the French.

Here's a small scan of your area of concern showing the detail available from the maps.

Image

look in the maps for sale for more info
http://www.mnr.gov.on.ca/en/index.html

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 Post subject: Re: Topo maps are unreliable when away from the travel routes
PostPosted: September 12th, 2008, 9:31 pm 
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Thanks, Smokey - that map would have been useful: I can relate now between what we saw and what's drawn on the map!

So, for bushwhacking away from the traveled water bodies - a 1: 10,000 map is the right tool!


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 Post subject: Re: Topo maps are unreliable when away from the travel routes
PostPosted: September 13th, 2008, 7:44 am 
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Resolution and being up to date....they do seem to make all the difference. The land is not static...it does change, often more than we realize...even if it is only vegitation and water levels.

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 Post subject: Re: Topo maps are unreliable when away from the travel routes
PostPosted: September 13th, 2008, 10:30 am 
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I don't think the topo map is really so far off - I think your interpretation and expectations are off a bit perhaps. The topo clearly shows a marshy area, which being green you interpret as forest. If I see the marsh symbol on the map and no contour lines crossing the area, I'm not going to anticipate any upland woodland. I'm expecting a marsh, which is what you found. That MNR map really is a good representation though and seems to accurately reflect the current situation without relying much on interpretation.

Cheers,
Bryan

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 Post subject: Re: Topo maps are unreliable when away from the travel routes
PostPosted: September 24th, 2008, 8:33 pm 
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The Ontario Base Maps are available online at http://www.geographynetwork.ca/ We have used them for some time.

Our experience has been that they often overestimate the amount of open water. A sort of average of the base maps and the 1:50000 topos is often about right. The improved elevation detail can be very helpful just the same.


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 Post subject: Re: Topo maps are unreliable when away from the travel routes
PostPosted: September 24th, 2008, 9:05 pm 
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D Burgess wrote:
The Ontario Base Maps are available online at http://www.geographynetwork.ca/ ...

I didn't know that - that is neat. I just pulled the area off there and that's what it looks like:
Image

Tomorrow, I'll show some photos that prove your observation about "too much water surface" drawn in...


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 Post subject: Re: Topo maps are unreliable when away from the travel routes
PostPosted: September 25th, 2008, 8:14 am 
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I have to agree with Erhard, on one of our Wabakimi missions I came across a lake (Scrag Lake) which had a nice size island with a campsite not too far from the main shoreline. This island was not on the topo map nor shown on my GPS! In canoe travel, this type of information helps us to identify where we are on the map. Being that this large island was not on the map, I am wondering if I could claim it for myself and put a lodge on it?

Barry

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 Post subject: Re: Topo maps are unreliable when away from the travel routes
PostPosted: September 25th, 2008, 9:25 am 
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Sorry Erhard, I don't understand your post 'Don't trust the detail of topos'

What detail is missing? All I see is some difference in the interpretation of Elm Lake.

What's your picture (Here's a picture of what 'it' looks like)? How does it not look like the topo?

I have never seen one serious deviation from a map and reality in all of my canoe travels. Yes occasionally islands are bigger, or missing b/c water levels change. Never trust a single blue line. Be wary of traveling in dry years based on a topo. (You can match a dry water along a lake to a map, and realize how low water is compared to a map - rivers are tougher.)

I've seen small beaver ponds disappear - but never decent size lakes. I've seen river meanders cutoff - but again, not a big deal. If you know where you are, you can recognize these deviations.

-Andy


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 Post subject: Re: Topo maps are unreliable when away from the travel routes
PostPosted: September 25th, 2008, 10:25 am 
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Sorry for sidetracking the discussion, but I'd like to settle a related matter, namely the accuracy of the topo showing a portage around Thunder House Falls on the Lower Missinaibi in Ontario.

Facts:
1. The Government of Canada topo available at the time (I have a copy) shows a dashed line on river right; it is marked POR, for portage.
2. Two paddlers went right and died; it is assumed that they were using the topo.
3. The canoe portage around the falls is on river left, as shown in Reid-Grand, for example.
4. NRCan Toporama does not show the cart track at all; it shows the portage trail on river left and marks it Thunder House Falls Portage. I assume it was prepared after the deaths.
5. There is indeed a cart track on river right, below the falls; we used it to portage rapids farther down.
6. The MNR Missinaibi River Canoe Route map (I have a copy)shows the portage on river left (1770 m).
7. It is not customary for Canada topos to show portage trails.

Questions:
1. Does the cart track extend to above the falls?
2. If so, did the paddlers who simply just miss it?
3. Is there (was there) any Ontario government publication with the portage marked on river right?
4. What responsibility, if any, do the Ontario and Federal governments have for the deaths, and I don't mean in a legal sense?

Can people here settle these questions, without reference to secondary sources?

Yours in paddling, Allan

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