View topic - Topo maps are unreliable when away from the travel routes

Many thanks to Erhard for posting the image of the topo; again, it is dated 1977, revised in 1978.

MNR:
The map in the MNR brochure of that time (undated, sadly no longer available to the public) does NOT show a trail on river right, from above Thunder House to just above Stone.
The portage around the falls is shown on river left, marked "P 1770 m". There's a note reading "Approach along left bank take portage entrance before small islands"
The portages around Stone and Long are marked as on the topo; distances are not given.

Reid-Grand:
They show no trail/portage/whatever on river right around the falls.
To an arrow pointing to a rapid above the falls is attached a note reading "Run with caution - stay close to left shore in preparation for portage."
The portage is marked "P1770", on river left; the map shows two starting points.
Stone and Long Rapids are marked "P1000R" and "P2000R".

Topo:
As remarked above, the topo shows a black dashed line starting well above the falls; the line continues almost to the end of Long Rapids. These lines typically denote cart trails.

I expect that the dark blue, dashed lines were entered in the 1978 revision. The indication "POR" is also in dark blue.

My notations on the topo:
The blue smudge was entered on the trip. We camped at the falls for 2 nights, maybe 3.

The red ball-point stuff was written in before the trip. That information is primarily from Reid-Grand (who I expect had the MNR brochure); not marked on the MNR map are the second starting point for the Thunder House portage, the camp sites and the portage distances for Stone & Long.
In those days, I was marking contour-line crossings (here 170 m and 160 m) on my maps; I omitted the 150 m crossing in Stone.
Below the falls portage, my red stuff overwrote some of the dark blue. I think though that the dark blue original can be seen.

Yours in paddling, Allan

_________________

If it's not worth doing to excess, it's not worth doing at all. (AJ)

Back to the Kawarthas back country.

Two more locations, "2" and "3":



Here's "2", looking north:

The base map gives you a good indication of what to expect in that low area SW of Pilot Lake, but 1:50,000 does not, it could be forest or just anything else dry.....:




and there's "3", looking west:

with a very similar level of reality presented by the maps. The 1:50,000 would not prepare you for this 500m ditch mostly filled with water. Am I boring you, guys? Ok, I knew that....

I am itching to know the answers. Am learning lots here!

_________________

Present: Slip, Slap and Slop, hide from the sun! Past: Get some colour in those cheeks! Paddle Naked!

That's my experience as well. I'm wondering what MNR means by "base" maps? I may be that the intent is to omit any vegetation. Marshy weed-clogged water tends to show up as open water on the base maps.

_________________
Old canoeists never die---they just smell that way.

Personally I like to reference maps as little as possible and find my own way. On a multi day trip I might check the map twice a day at most. Some people I've canoed with have their nose in the maps constantly. Relax man! Even worse than that are GPS addicts. Put down the gadgets and take in nature.

Sure, that's a good way to make the most of your trip.

But this thread is about the characteristics of a tool that we use for navigation: it's about the potential and the limitations of the 1:50,000 Cdn topo maps. And there were some good replies and observations by various folks - I thought the issue was worth discussing. And I picked a subject heading that got your attention...

_________________
“What is the good of having a nice house without a decent planet to put it on?” - Thoreau

I spent 30 years working in the government department responsible for the production of the Canadian Federal Topographic series of maps.

Not all topographic maps were / are created equally, regardless of the series.

A better way might be to say that the methods used to measure terrain features varied across Canada over many decades and due to the often extremely difficult landscape, several different measurement technologies were utilized in different regions of the country.

As an example, a branch of the Department of National Defense called the Mapping and Charting Establishment (MCE) used the Canadian Arctic as a training location for military mappers and navigators and produced the majority of aerial and ground survey data that was used to map the north decades ago.

Also because of the size of the landmass, the frequency at which any area would be resurveyed or remapped also varied (and varies dramatically). Note the dates of issue on any topo map and you'll get a good indication. It would be impossible to produce a 100% accurate real time map of this country.

The philosophy, at the time, was to resurvey and remap areas more frequently that changed most rapidly - aerial survey would get flown over Toronto every few years but Moosonee might get flown every decade or more. So there is this huge disparity, at times, between the quality of maps in some of our highly developed urban areas and our less devloped remote areas -- the places where all us paddlers like to head to.

Of course, in later years with the advent of satellite surveying, GPS, better earth modelling and a number of other methods and technologies map products are becoming more accurate in our wilderness areas.

But, it was always amazing to me, how accurate the photogrametrist was, who sat at his desk with a pair of sterographic glasses on and interpreted the Aerodist survey photos and related them to ground control markers. Those old survey methods may have been old but they were often surprisingly accurate.

A job that crossed my desk at one time was to readjust the elevation of Mt. Logan - for the 90th anniversary of the Geological Survey. I combined the earliest survey work done with pack mule and climbers, surveyors who sat on adjacent peaks for days observing by triangulation methods over many hours ....... with a modern GPS / Satellite survey done over 24 hours. The adjustment compared data sets of the old and modern methods and final elevation results were within +/- 1.5 metres.



Dann

Thanks for these insights - representing nature on a map is a form of abstraction. In my early days of paddling I was surprised how accurate each indentation in the shoreline etc was represented where I paddled and thus navigation was possible by detailed comparison between map and nature.

Later, when traveling more off-route, I was surprised to find differences. First I attributed it to less care on part of the map maker because hardly anyone would go there. But later - especially after this discussion - it became obvious that shorelines etc typically are more complex once one gets away from the "easy" canoe routes. I should mention that I am a fan of maps - they have always fascinated me...

_________________
“What is the good of having a nice house without a decent planet to put it on?” - Thoreau