geotagging old aerial photos

PIX4Dmapper PIX4Dmapper Questions/Troubleshooting
1

Hi,
I have a set of aerial photos with overlap took by the US over Noumea, capital of New Caledonia in the year 1954. focal length should be 125mm, position (lat/lon) of the center of photo, altitude, run directionand nominal scale has been deduct from focal length. These localisation data are stored in a mid/mif file. I would like to geotag these files to process them thru Pix4D Mapper to produce a seemless image. Somebody can indicate me a software that will allow me to create un exif header from these data (that I’ll manually capture). My files are Tiff, but I can convert to jpeg if needed.

Bonjour.

J’ai un jeu de photos aériennes avec recouvrement prises par les forces US en 1954 sur la ville de Nouméa en Nouvelle-Calédonie. L’IGN, propriétaire des données, m’a communiqué un fichier d’assemblage (mid/mif) avec pour chaque image; longueur probable de focale, position (lat/lon) du centre de la photo, altitude, direction de vol et GSD. Quelqu’un pourrait me conseiller un soft qui me permettent de saisir ces informations et d’ajouter un header exif à mes photos afin que je les traite avec Pix4d Mapper pour obtenir une seule image seamless.

2

Hubert,

We see two points you could address for such a project: 

  1. Camera model

As the camera model is not in our camera database. We would create a new camera model based on the available information (focal length, resolution,…) and create a new calibrated model. This article describes how a camera can be calibrated and added to the user camera database: https://support.pix4d.com/hc/en-us/articles/206065716 

  1. Image geolocation

In order to add the geolocation, we see two possibilities: 

a) write the image geolocation in the EXIF of each image

For this we would have a look at the following tools: 

b) input the image geolocation as external .txt file

The image geolocation can also be entered as external .txt file. The format would be: imagename, latitude [decimal degrees], longitude [decimal degrees], altitude [meter] 

This might be easier than tagging the image geolocation in the EXIF of the images. More about the format of input files in this article: https://support.pix4d.com/hc/en-us/articles/202558539-Input-Files#label2

Here is how these can be imported: https://support.pix4d.com/hc/en-us/articles/202560019 

Let us know how it went. :slight_smile:

3

Thanks for these usefull answers. I’am going to use a text file to georeference the photos. The photos have been took in 1954 with an argentic technology on 18x13 negative and have been scanned for a finale image at scale 1:10.000 at 400 ppp. for ex. a typical photo is 2814x2055 pixel representing 1787x1305 meters on the ground and 17,87x13,05 cm at 1:10.000 print scale (400 ppp).

I don’t know what value I should enter for camera model in :

  • Sensor Width [mm] or Pixel Size [um]: Set either the sensor width in millimeters or the pixel size in micrometers.
  • Focal Length [mm]: Set the focal length in millimeters.

The information that I have about the focal lenght is 125 and a format of 170x120. I think these is not usefull as original negative print has been scanned.

Should I put as sensor width the size of the scanned image (178,7mm) or 63,509 um ? and what focal length ? 0 ?

best regards

4

Following a calculation with the data that I have. Results are not far from what I should have (1858 vs 1787 ground meters and 66,04 vs 63,5039 gsd) and it’s the perfect values if I say 130 as focal length ??? may be that’s the thru focal.

 

5

It is difficult to say what the correct values are as there are a few unknowns from the original camera and because the images were scanned afterwards. We would use the values that you have computed as initial values for the processing. Then, we would load the optimized parameters that were computed by the software (in case the result is acceptable), so as to get closer to the “real” values of the parameters. 

Have you had the chance to setup the camera model in Pix4D Desktop and do a reconstruction?
Feel free to post screenshots of the results, or a link to the Pix4D Cloud project if you have.