How to survey 101

[darkplaces]

Surveying's fun and exciting. 

It is when you found something new(ish)  or want a survey you can publish without copyright issues. I like filling in the details like '5th Sep 1896' written on the wall.

ooPS I had forgotten things like MAG to GRID getrid and GRID to MAG add. Everything is MAG so trying to overlay it would be all a skew by 6deg.
The check angle is a good point as I would hate to be using a bad compass and not know it.

Walrus's experience of the survey software mirrors mine.

Cheers for the info so far, glad I asked now.

 

[Dep]

...
ooPS I had forgotten things like MAG to GRID getrid and GRID to MAG add. Everything is MAG so trying to overlay it would be all a skew by 6deg.
...

Be careful, the error is much less than that and hanging noticeably over time.
It was about 6deg when I first learnt about this as a teenager,nowadays it is closer to two deg IIRC.

OS 1:50K will give angle, date and expected change over time.

At some point in the next few decades the error will reduce to zero before starting to increase again.


I downloaded survex last night and started playing with it.
A very simple and nice program, but the example posted above contains errors so this may be why there is confusion with the program, it does not build a .3d file.
But remove all but the data and it works ok.
Also you have to RIGHTclick the .svx filke and select 'process' to build the survey.

A great piece of software - very impressed.

 

[Dep]

Modify has gone AWOL....

Be careful, the error is much less than that and hanging noticeably over time.

I meant to write...

Be careful, the error is much less than that and changing noticeably over time.

 

[Peter Burgess]

DP's point about using a check bearing to check your compass against a map is good. Forgot to mention it earlier. Also useful if you use a different compass - check them against each other.

 

[graham]

DP's point about using a check bearing to check your compass against a map is good. Forgot to mention it earlier. Also useful if you use a different compass - check them against each other.

It's not good, Peter, in any survey with pretrensions to accuracy, it is essential. Every compass will have a built-in error of a couple of degrees and magnetic variation will account for a fair few degrees more (or less if the errors cancel out slightly.

What is more is that magnetic variation can vary on a daily basis so, for surveying purposes, every compass needs to be calibrated against a known bearing every time it is used.

 

[Peter Burgess]

Don't forget that local gravitational anomalies may affect your clino.  In particular, if your surveying helpers are extremely obese. 

 

[darkplaces]

Oh gawd now its getting all complicated glad I currently don't feel the need to survey caves  just nice big straight line level mines hmmmm scrummy. Were aiming for SMCC Box type surveys but with loads of detail like 'really old fag packet here'... Its a bit of fun and might produce something useful.

 

[graham]

Don't forget that local gravitational anomalies may affect your clino.  In particular, if your surveying helpers are extremely obese. 

Har har very funny. The fact of the matter is that a combination of compass error and mag variation can add up to about 12 degrees. That is clearly not acceptable in a situation where instruments can be read with a precision of 1/2 a degree.

 

[Peter Burgess]

Check that steel-framed spectacles are not affecting your compass bearings. This one is a serious comment!

 

[Walrus]

I downloaded survex last night and started playing with it.
A very simple and nice program, but the example posted above contains errors so this may be why there is confusion with the program, it does not build a .3d file.
But remove all but the data and it works ok.
Also you have to RIGHTclick the .svx filke and select 'process' to build the survey.

But... that implies I have to read some instructions  :blink:

I'm also going to have a play with a CAD application I've got (TotalCAD - comes free with cornflakes) as you can specify survey type angles & distances and get it to plot them using the GUI. Not looked at 3D versions yet.

 

[axbridgecaver]

Hi Darkplaces

I can come along to your site with the ACG surveying gear (compas, clino and tape) and give you and your friends a teach in on surveying. I have created an excel spreadsheet you just type the data in and out comes the plotting co-ordinates.

Then the difficult bit - I always hand plot the survey - I think the computer generated surveys are poor and a much better looking survey can be achieved using this method. Just my view. It does take time to hand plot and a large drawing board. I then scan the plot and electronically trace the survey then all the information and detail can be added.

PM if you wish me to come along.

 

[darkplaces]

Hi Darkplaces
I can come along to your site with the ACG surveying gear (compas, clino and tape) and give you and your friends a teach in on surveying.
PM if you wish me to come along.

Ahhh thats very kind. I shall have to consort with my team mates. Are you free weekday evenings from 19:30hrs?

 

[paul]

Check that steel-framed spectacles are not affecting your compass bearings. This one is a serious comment!

And your helmet-mounted light - espcially LED types with electronics...

 

[Walrus]

Check that steel-framed spectacles are not affecting your compass bearings. This one is a serious comment!

And your helmet-mounted light - espcially LED types with electronics...

So if surveying I'd be better off using something like an FX5 (no fancy electronics)?

 

[menacer]

I tried this application on two XP machines; one wouldn't run (kept getting a DOS error) and the other ran but wouldn't read the supplied test data. I'll acquire a copy of Visio and try DP's method!

Sorry walrus, got home and just tried it, try the same using this

*begin box

0 1 3.8 225 0
1 2 5.4 256 0
2 3 12 312 0
3 4 6.2 360 0
*end box

 

[paul]

Oh gawd now its getting all complicated glad I currently don't feel the need to survey caves  just nice big straight line level mines hmmmm scrummy. Were aiming for SMCC Box type surveys but with loads of detail like 'really old fag packet here'... Its a bit of fun and might produce something useful.

Have a look at http://cucc.survex.com/expo/handbook/survey/what.htm for a bit more general information on cave surveying.

 

[Dep]

Check that steel-framed spectacles are not affecting your compass bearings. This one is a serious comment!

And your helmet-mounted light - espcially LED types with electronics...

So if surveying I'd be better off using something like an FX5 (no fancy electronics)?

Yess indeed, whilst helping Peter once I had about a degree of variation in backsight readings depending on whether or not I had my helmet on.

 

[paul]

Check that steel-framed spectacles are not affecting your compass bearings. This one is a serious comment!

And your helmet-mounted light - espcially LED types with electronics...

So if surveying I'd be better off using something like an FX5 (no fancy electronics)?

No use a brass carbide stinky!

The thing to do is to test out any interaction between your light and the compass reading - whatever the light. It does seem that headsets with LED/electronics are more prone to the problem.

 

[SamT]

or better still - tape a small flouresecnt light stick (available from fishing shops) over the compass and hey presto - self illuminating compass/clino - no need to have your lamp anywhere near it (i.e. take your helmet off to take the reading.)

 

[graham]

Then the difficult bit - I always hand plot the survey - I think the computer generated surveys are poor and a much better looking survey can be achieved using this method. Just my view. It does take time to hand plot and a large drawing board. I then scan the plot and electronically trace the survey then all the information and detail can be added.

The late and extremely lamented, Mr Irwin used to complain vociferously to me about the standard of survey presentation in recent years (decades). He maintained - and I wholeheartedly agreed - that although you can get the magic numbers box to calculate the co-ordinates and even plot them - the final presentation must be done by hand as only that way can you get something that can be properly understood by the user.

Doubtless some of the computer geeks would disagree with me but there is, as yet, no survey drawing program that is both straightforward to use and pleasing in its results.