Topics

1

General / Flir Thermal Model

« on: August 13, 2016, 11:14:39 AM »

Hi All,
Having a problem. I am using a Flir Vue Pro to shoot some aerial photographs of archaeological sites. I have seen photoscan be used by other people, but when I try to run it, it just can't seem to produce an alignment. It is saying that the cameras have been aligned and I can get a point cloud of around 60 000 from them using highest settings. It will show points on the screen but not a scene as such, nor camera locations.

The Vue Pro is low res (640 × 512) and I am filming scenes as jpeg files as black/white hot. I have plenty of overlap and am taking hundreds of photos.

Can anyone offer any advice as to settings? I also have a regular photographic model of the same area and I have multiple GCP's. I am just not sure if its the fact that these black/white images are just not different enough, or if I am messing up something in processing as I have seen people creating models from thermal before including in B/W.

Any help would be amazing!

2

General / Accuracy of measurements

« on: October 24, 2015, 08:18:35 AM »

Hi All,
I am an archaeologist and I am testing photoscan for the creation of ground plans. I just want to make sure I understand one aspect of it.

One test I did was to place a L shaped piece of metal with 3 known distances on it(quite small, like 0.35m and 0.55m). I use the right angle of the markers on the L in order to produce an orthophoto of the area using them as the horizontal and vertical axis, in order to get a perfectly flat birds eye view.

Anyways, I input the distances into photoscan, create scale bars and get a minimal error of a few mm.

Now to test the accuracy of just using these two points on the L piece, I placed a few control groups of marks anywhere from 2-5m away. These were either 1 or 2m in length.

What I want to know is- what is the error produced when just using the L shaped piece with 3 measurements. Obviously as you add more scales, it gets more accurate.

I think if I create markers for my control group points, then create scale bars and enter the distances (1 or 2m), it will provide me with the error. I just want to check that I do not UPDATE this, as if I did it would modify the error with all the scale bars correct?

So just to get the error using the 3 points on the L, enter distances and hit update. Then to get errors of my controls enter distances but do not hit update. Correct?

Thanks in advance for what is clearly an easy question- I just want to make sure.

3

General / Archaeological Planning using Photoscan- without GC

« on: March 25, 2015, 05:45:39 AM »

Hi All,
I, like a number of folks here, am an archaeologist and I have used PS to create models of archaeological remains- although I am fairly new. I am after a bit of help with a workflow for something slightly different.

Here is the situation- on a couple of projects I have been on, I have created top down plans of archaeological features using photoscan and a total station to give me GCP. Basically, I create orthophotos which I trace off in adobe photoshop or illustrator. The plans end up looking like this(http://www.twoatlarge.com/illustrations/tower_1.jpg) nb: thats not my plan and just shows what an archaeological plan will look like if you don't know. I will sometimes make models without a total station but will mark on the stones a series of measurements ie I will put stickers on that are 1m apart to give me a scale.

I have been asked to look into using this sort of skill on things such as rescue excavations, where we have a day or two to dig an area and require a plan, but often not the time to do this properly. The big issue with this is that generally there are no total stations or anything to give me x,y,z coordinates. I can us a theodolite to get heights(z) though.

What I need to do is to produce an orthophoto that is a perfectly vertical/birds eye view of the building, wall , feature etc like the example above. What I am curious about is if anyone can suggest a way I can get this perfectly vertical orthophoto without just trying to guess what is vertical? With GCP points from a TS- it obviously knows what is flat and produces a nice orthophoto, I just cant work out how to do it without GCPs.
 I would then use stickers or markers at set measurements to provide scale so in that sense it's fine.
 I am using PS Professional.
If anyone can offer some advice, or if there are any archaeologists out there doing this, I would love to hear from you.
Thanks
Hugh