I agree pretty much with everything said in this thread - I have (for now) pulled out from survey work partly because of the pricing issues - the advent of new computerised equipment has simplified fieldwork and largely automated calculations - output in \cad etc. \but because the work is...
Irstuff is right - I have heard that some people use two GPS receivers on the plane/helicopter (both ends)for instance thus helping with the orientation etc- this then gets referenced to the camera-
Hi
Have you considered some photogrammetric techniques? With the right stereophotography setup one should be able to get this sort of accuracy. Contact a local photogrammetrist or failing that speak to some instrument manufacturers like Leica which specialise in this area. - good luck.
No but surely a digital camera like that would need a refeence frame to work from as well as "knowing" whether it is pointing up or down - so that would require some sort of sensors - GPS etc. I have only come across this type of setup in combination with theodolites - or GPS - One...
Hi,
I generally agree with all your comments but warn against using two points only as you will get a seemngly valid result from two points but if one has been tampered with the consequences can be dire so check and check again three undisturbed points or benchmarks are advisable. Manholes have...
Hi,
I do not have too much time to answer this but suggest you look at LEICA instruments website - they manufacture high precision Laser machines which are used to model surfaces etc accurately - see their high precision instruments-if need more information end a reply and I shall follow up on...
I have no idea but being a surveyor in our parlance azimuth is the direction (or angle from true north or south depending on which hemisphere)
Sometimes azimuth is referred to magnetic north and hence the variation between true north and magnetic north may possibly be regarded as the azimuth...
Hi,
There are optical plummets available which will do the job - See typical surveying instruments websites such as LEICA, Optron, Sokkia etc. Alternatively a LASER can be used as a plumbline reference - This yields a visual line which cabn also accurately be measured with a special sensor.Be...
There are also survey techniques which can be used to monitor movements of buildings using a Total station with distance measurements to targets - some use lasers.
Your local surveyor should be able to advise on this in more detail.
Irstuff is correct with his response - Accuracy will depend mainly on price.
Handheld GPS such as Etrex etc are relatively cheap but will give at best around 5m - more usually 15m accuracy - Height is usually the worst.
There is a system called WAAS which claim to give accuracies to around 1m...
As a layman in this area (since I am A Surveyor - Geomaticist) I can suggest: albeit a bit late in chipping in but instead of ultrasonic sensors I could suggest using or adapting a laser distancer such as the Leica Disto - This can be mounted and electronically wired to give depths. It depends...
Handheld GPS to 100mm! Please let me have the name of that instrument?
Total stations are usually adequate for most site work and have the added advantage to be able to measure under cover etc which GPS does not - Beware of Multipath errors on GPS.
If you do drive around a site with GPS...
Quite right,
The danger lies in the matching of differential surveyed points from different reference points. Also whether there is an overlap of control points taken from different reference points/ different observation procedures / and possibly affected by ground reflections(multipath etc)...
I know this is a bit late but the answer given for this question is the most basic and dangerous.
Lat Long by GPS is based on Ellipsoidal approximations of the earth's surface.
Usually GPS receivers get positions on WGS84. There are standard fromulas available to convert to Y-X-Z ie cartesian...
As a surveyor I wholeheartedly agree - It depends largely on the input survey method etc.Also the precision to which the computer rounds of data is critical.
In general you could have a rounding off to say 0.01m over one hectare that could make a considerable difference to your quantities -...
I am not sure what the scanning is for but have you considered laser scanners like CYRAX, CAllidus, Riegl etc.
These will yield a "cloud" of points in 3-D with approriate conversion to CAD one can then use this data for spatial analysis.
Yes that is theoretically correct and accepted practice I however query the accuracy obtained physically from the actual position of the vihicle on the terrain - if it bounces around you may well get a spotheight of a point above the ground for instance. Also how frequently are spotshots...
SC
Sounds quite interesting what you are doing but I would be more interested in knowing which GPS you are using and in what mode - Heights on a moving vehicle - how accurate are these if vehicle bounces? Are you using two receivers (one being stationary) Your results may possibly be adequate...
Your heading refers to navigable river - this may have an effect on ownership rights as well as the boundary position.
I can answer your query fully in terms of South African law but it may not be relevant to your problem -
Please advise if that would help you.
Hi,
This is from an engineering point of view out of my league but read all this with interest. I am a Land Surveyor specialising in deformation surveying of structures.
Does the client perceive the vibrations still now. Then surely one should be able to measure it. From the description this...
