# Attaining real scale

Good morning,

I am taking images with an inspire 1 and have been using the “Explorer” version to get familiar with the workflows. I am currently working with full demo trying to prove to management that this is a good solution for our workflow but I am unable to extract meaning full dimensions.

I am in USA. I am wondering what would be the best coordinate systems to use.
To give you an example,

An length measure in the point cloud measures 65" whereas in real life that distance is 47". However the more look proportionately correct.

How can I solve this issue.
Thanks

You have to give your project a scale. So you will need to know the measurements of something in your project.

Ryan, I do know some measurements. I have tried GCP and event set them to act as CHECKPOINTS.
Unfortunately I do not have access to a Surveying Rover/GPS. I would love to know how to scale a raycloud based on set of know dimensions.

Check out the webinar on indoor mapping. About half way into it they set the X and Y distance, you have to set it to a 3d gcp and from there it will scale after re processing.

Thanks Ryan,
I will look at it and see it helps me overcome this challenge.

Here is the link for future reference:

Not as easy to execute as in the video but I am getting there.
So I was able to replicate somewhat of what I saw in the video to define the Z scale and somewhat of an orientation.
However the project still a little lop sided X and Y plus the Polygon across the driveway is still 4" short from the real dimension. It should 8.90FT where I should be at 9.2FT
Show I be able to also convert those points to 3D GCP and set them a dimension apart and maybe define a horizon?

http://s10.photobucket.com/user/Profoxcg/media/3DGCP_zpsn54qyzkx.jpg.html

I have a question about workflow:

I noticed that it is very hard to select points that describe a true physical point of reference (the edge of a wall for example) with out a Densified point cloud. So I am guessing the it is best to run a rough Initial processing and Point cloud and then use the point cloud to add Control points etc to scale the dataset. At that point, the data set can be reprocessed at a higher quality for manual feature extraction and measuring. Am I on the right track?

I still would like to know how to define the X and Y axis.

BTW, how do CHECK POINTS compare to the what I am currently doing?

Can you share how to get the “pix4D Capture” app to connect with inspire?

Hey Floyd! I don’t think that the app is already available for the inspire1. According to pix4d it should be in May.

Sorry for the late reply. I do not think the app is ready yet, but I could be wrong.
I capture my data by flying “by hand” and carefully selecting my shots. I do not think the app will be much help when doing non ortho.

Hi DDS CAD, about your workflow, you can as well after step 1 just reoptimize, if all or almost images are calibrated and quality report is not bad, then you do not need to process again.

Check points are not used to increase accuracy, they work in a different way than GCPs, check points are used to measure the accuracy of the model by measuring the difference between the the location of the point in the model and the the location in reality.