Agisoft Photoscan

We've been using it for three years; we also use Pix4D when we are working with another firm in conjunction with jobs they have done. Generally for survey Photoscan is good, few bugs, does what you would expect. The accuracies are generally good; obviously if you have a decent amount of ground control that tightens things up.

ID'ing the ground control is a little slow, but it does give you all the photos for each point in one screen, so you can check them quite quickly.

It is unusual for Photoscan not to be able to resolve image tie ups, but occasionally it struggles with tree canopies (presumably because the leaves are blowing around between adjacent frames) and you probably won't get much if whole frames are just water - but that applies to most software. In calm conditions and clear water we have found it will resolve underwater detail down to around 3-4 ft.

Powerline conductors can sometimes be a little bit of a struggle, so we find that setting one run directly above the line helps.

Photoscan has a tendency to round off sudden changes in grade, for instance against a hedge the ground will be curled up, rather than giving a straight break line. We get over this by using our survey software for digitising strings direct from the orthophoto for position and then heighting them using nearby points from the 3D cloud, where we can see what is going on. We export the general ground heights as a high density grid (depending on the job at a spacing of 1-5 metres) into the survey software and then thin out once the strings are overlaid.

Once you get your head around how Photoscan filters then eliminating non-dtm points is fairly straightforward.

Updates have been made on a regular basis. You pay only when there is a full new version released, general updating is not charged.

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Thanks for your review Chris, very thought out and helpful.?ÿ