SAE’s 2024 World Congress Experience (WCX) was held this week. Unfortunately, I couldn’t attend as I was galivanting around Spain with the family (hence the two-week newsletter hiatus). However, our colleague and my good friend, Jarrod Carter, has been kind enough to share some of the highlights via his LinkedIn feed, which is where I caught wind of this week’s topic. Thanks, JC.

Performing photogrammetry analyses with iPhones

Nowadays, a notable portion of the photos we receive for analysis are taken with an iPhone. This shiny new paper, authored by Joseph Neal, Tara Leipold, and Karla Petroskey, informs us that all iPhones since the 7 are equipped with optical image stabilization (OIS) that cannot be deactivated. PhotoModeler advises users to turn OIS off when calibrating cameras and further recommends that the max residual during camera calibrations is below three pixels. Of the seven iPhones calibrated in the subject study, only one had a max residual of 3.0, the rest were between 4.8 and 8.6 pixels. So, with perma-OIS and higher calibration residuals, can we reliably use iPhone photos for photogrammetric analyses?

Fortunately, yes. When compared to FARO M70 data, the median residual between the scan data and photogrammetric solution was 3 mm when the iPhones were calibrated and high-contrast targets were placed on the vehicle. 95% of the residuals were between 1 and 11 mm. When an exemplar calibration was used (same make and model iPhone, but not the EXACT same iPhone) that median residual remained the same and 95% of the residuals were between 1 and 12 mm. So, OIS doesn't prevent us from using iPhone photos. Further, the results indicate the technique of using exemplar camera calibrations to estimate camera parameters is sound. We have a paper in the hopper at Lightpoint that will build a bit on that concept.

I recommend reading the full paper here and sticking the reference in your file any time to you perform a photogrammetry analysis based on iPhone photos.

It’s good to be back, I hope you all have a great weekend!

Lou Peck
​Lightpoint | Axiom