Perfect XYZ align without GPS

[AdrienB]

Hello everyone,

I work in a company who use Agisoft photoscan pro,
I'm in charge to do a work, and I have a problem,
I searched in the forum but didn't find a solution.

I use a DSLR without GPS and i have to do an orthomosaic to draw a blueprint with draftsight.
to do this blueprint my model have to be perfectly aligned on the 3 axis before create the photo.

Easy with a GPS but without ...
I wondering if there is any solution to align like that ?


Or maybe a tips, to prepare my scan in " real world ", that could help me to align ...

Thanks everyone,
Good day

[stihl]

What you could do is create a local build Orthomosaic (un-referenced) and then use a GIS like GlobalMapper to manually position the Orthomosaic based on a Google Maps overlay or some other public source.

What kind of accuracy are you aiming/hoping for?

[AdrienB]

Hi stihl,
Thx for your quick answer,

Its not an aerial orthophoto, i scanned an object wich is about 8m height, 4m width and 1m deep so it will be difficult to use your solution ...
I need the best possible precision, some people will work with my blueprint so if it's wrong  !


EDIT :

is it possible to create something like 3 physical spot ( before scanning ) take their coordinates, create some " repères "  ( flags ) in PS, switch in WGS84 and then put the coordiantes.
Did my pointcloud will be aligned on earth coordinates ?

[frank.stremke]

hi if your model is on even ground i would recomend use markers stiking to the ground as a preparation use some targets or the one photosan provides print them and stick them on the ground with sticky tape then do a systematic survey by whatever instrument you have
you can just use a tape meter since it is all flat you dont have to wory about the Z axis and if you are a litle bit up in your skils you can simply do a trilateration network in between the points
https://en.wikipedia.org/wiki/Trilateration
this is super easy and you dont have to calculate it just start measuring and then use circles (and thier intercepts) in draftsight to draw a map of your points finaly extract to coordinates for this points from draftsight into a csv file
then start photography and in agisoft import the csv file as a local coordinate system (dont use wgs it will do al kind of crazy projection stuff and think that your model is 8degrees long ;-) )
in the local coordiante system place the markers on the photos and optimize ---- DONE
as easy as 123
frank
 

[Gall]

Hello AdrienB,

if you don't need to have coordinates of the scene maybe you can try the scale bar optimization with the known distances of your object (as described in the user manual p45).

[AdrienB]

Hi Gall,

Thx for your answer, i've ever done what you said, but it's not what i'm looking for.
Maybe my first message is not clear, my english is not perfect.

I'm looking for a solution to align my model in xyz axis, exemple, when i clic on "1" (numpad) i'll be perfect ( as possible ) of my object.

frank.stremke

Thx you, im not sure i've all understand ( the part of work on draftsight ) but i'll try to read again and understand. Then i'll try again my work.

If i understand :
- Before scanning :
Use PS markers on the ground around my object. mesuring distance between points, then open DS and draw points were my markers are ( still on XY only with a relative positions ) then, export in CSV to import in PS.
- After scanning :
Import CSV in PS, it will understand that is a map for markers with the " local coordinate system " tools.
Then put markers ( flags ) on the real world markers ( after aligning photos i guess ? ) and then, my view will be " perfectly " aligned with XY ( then Z will be deduced ) so, like a work did with GPS exif photo, my object will be aligned on XYZ and at the good scall ?

I understood ? 

Good day !

[Alexey Pasumansky]

Hello AdrienB,

You can use Planar projection type in the Build Orthomosaic dialog and use Markers option to define the projection plane. For example, having three markers would be sufficient, if you can put them on the plane that is parallel to the desired projection plane.

[frank.stremke]

yes this sounds good your coordinates wil have x and y and all the z coordinates will be 0
to draw this and create the map in DS
start with one arbitrary point and measure the distance to the next draw the line in draftsight with the same legth
this is your baseline
now measure from point 1 and 2 the distance to point 3
draw a circle in draftsight with the radius of the measurements from point 1 and 2 to 3 the circles will intersect in 2 places select the corect one and place point 3 in the drawing then you can move forward to point 4 and so on
frank

[AdrienB]

@Alexey
Thx, work fine ! my blueprints are good

@frank
Okey, i'll try to use your way, i'll do a post after
Thx you too !

[pedram55]

Hello
I have same problem .
Suppose  control points are 4 and located in 4 corners of a polygon  and my object located between them .
I measured  distance between 1 to 2 and it is 30 cm . i haven't measured other distances . i am going to set point 1 coordinate as (0,0,0 ) and according to measured distance for point 2 (0,0.3,0 ) and define coordinate system . but when i do it and change coordinates of control points (number 1 and 2 ) nothing happen and other control points coordinates value remain on previous values and model position doesn't change .
please tell me what should i do ?

[Alexey Pasumansky]

Hello pedram55,

After you perform any changes to the coordinate information to the instances in the Reference pane (or introduce new reference points) you need to click on Update button on the pane's toolbar, providing that all the instances that you wish to use for the referencing and scaling are checked on in the pane.