Techniques > Navigational Questions & Answers

Getting a fix using the angle of the slope

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captain paranoia:
> Where the lines intersect is your position and you can read off the height from the figures on the contour lines. No need to use a slope angle tool. Itís probably a quicker method and certainly more reliable.

But if you can perform a resection/triangulation, you won't need to use slope aspect & slope angle or height to find your position...  As Lyle says in paragraph 2 of p156: "if you are relocating using slope aspect, you probably have a poor GNSS signal, so don't use its satellite altimeter"; in other words, slope aspect & height are somewhat 'last resort' solutions, and other methods are preferable and more accurate.  It may be that you cannot see remote landmarks to perform a resection (as in Pete's earlier example).

Pete McK:
Spot on Captain. It is neither a mainstay technique nor one which should be used in isolation. But in certain circumstances, such as those frequently encountered in the Lake District, sudden low cloud and reduced visibility, the technique, in combination with slope aspect and terrain association, works well :)

Hugh Westacott:
Some of you may have noticed that this thread disappeared for a time because exception was taken to the tone of some of my contributions to the discussion. At first, I was taken aback because I had no intention of being either offensive or disrespectful, and it was only when I read them again that I realized that they could reasonably be described as abrupt, even abrasive. It happened because I was cross with myself as I seemed unable to describe sufficiently well the point I was trying to make.

In a previous career I had to write abstracts of articles. The art of abstracting requires an article to be described accurately and dispassionately and in as few words as possible, so adjectives and adverbs are used only where absolutely necessary. This technique, although useful to clarify one's thoughts, is not suitable for use in a forum post.

As the police would say, I've been given words of advice! My contributions to this thread have been edited to make them more emollient yet still retain the points I was trying to make, and I have sent a private apology and explanation to Lyle.



Now that we have come this far into the discussion, I relate this experience. Not long ago,I took an off road walk onto a wooded ridge, with a  1: 50 map. I always knew my approximate location, but could never get an exact fix, Even tho there are plenty of landmarks in the distance, to get a bearing from, the ridge is heavily wooded, so visibility was restricted to the nearest thicket of down slope tree tops. The  ridge was more or less of like aspect in any given section of the walk. I came to a point where I was trying to reckon when to turn onto the next leg, but found that I had not gone as far as necessary. It did not go as planned, but I was able to follow the ridge to my starting point. If I had been trying to reach a specific location, I'd have been lost, or doing some exploratory work. That night, I spent some time at reviewing my route, with Google maps [all those trees] but I could not be certain of my exact route. I did mark my path on the way in. In short, knowing the exact location is not as important as knowing the general route & lay of the land, but it can make a big difference.  :'(


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