element of imagination and creation

How is photogrammetry defined?

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If you’ve never heard the word “photogrammetry” before, I wonder w… No. I know very well why you’re here.

Even though “photogrammetry” is quite an old word (not much younger than “photography“) it is still weird to use in common discussions with friends or colleagues that are not familiar with this field. They’re like “oh, photo…! Wait, photo-what?”. Hell, even the text editors’ thesauruses are failing to recognize the term (I always have to add it to dictionary).

What will I learn in this post?

Basically you’ll learn the most used definitions of photogrammetry in literature, but with a little extra:

  • What does this term actually mean
  • Photogrammetry: The Origins
  • Were there any term variants?
  • The usual definitions the experts are using
  • And, of course, my favorite definition

While I won’t dabble now into the theoretical aspects of this method (I shall discuss these in following articles) and what it actually “does”, I’m only going write about the various perceptions of this method and some bits about the history of this term.

So where does “photogrammetry” actually come from?

This term was coined by Albrecht Meydenbauer back in 1867. It was a combination of three words:

  • photo” – from the Greek root word “phos”, which means light or a process obtained with light or the radiant energy of light.
  • gramma” – also from a Greek root, “graphos (I write), means “letter” or the drawing of the symbol/image of the letter
  • and “metrein” – meaning “to measure

So a full literal translation would be “Light drawn data measuring”.

This term seems a bit complic…

Oh, right! While it might seem complicated to brag in front of your friends about your extremely rare expertise by using this term, you should know that we got away with it quite cheap! There are several other terms coined by other “fathers of photogrammetry”, terms that did not quite catch to the ear. Or rolled too much tongue in the mouth.

So, what have we missed? Let’s see:

  • planchette photographique (Auguste Chevallier – 1858)
  • ikonometrie (Aimé Luassedat ~ 1859)
  • photometrographie ( Albrecht Meydenbauer – before 1867)
  • photographometrie (Ignazio Porro – 19858)
  • phototopographie (Pujo & Henry George Fourcade)

Short commentary: I just couldn’t find any reference to this Pujo. I barely found out about Fourcade. Apparently, everyone uses this list as is only with their surnames.

Meydenbauer believed that the quality and accuracy of direct measurements of buildings (for building surveyors) could be improved by using indirect measurements from photographic images. He even developed his own apparatus and lenses to prove his theory.

This idea came after he had an accident that could have been fatal during some building measurements. The year was 1858.

Albrecht Meydenbauer in 1909, at his retirement
Albrecht Meydenbauer in 1909, at his retirement

But only during the summer of 1867 he had the opportunity to test his own camera on the town church and the surrounding fields of Freyburg-on-Unstrut (near Berlin). It was then when, together with geographer Dr. Otto Kersten, they came up with the simpler term of photogrammetry.

Despite his good results, it was only 25 years later that the Prussian Parliament House was convinced that photogrammetry was a reliable and accurate method for the documentation of cultural heritage objects. So much so, that Meydenbauer received enough funding for the establishment of a Photogrammetric Institute, with him named as director. The Royal Prussian Photogrammetric Institute.

The year was 1885 and we had the first photogrammetric institution the world.

Principles of photogrammetry by Albrecht Meydenbauer
Principles of photogrammetry, as promoted by Meydenbauer

Ok, got it. What about today?

Well, today we are witnessing an explosive re-emergence of photogrammetry as it is now available to the consumer public in integrated solutions. I’ll cover more about this in future posts. But to conclude this one, let’s see how photogrammetry was defined up until today.

A direct search on the most popular search engine today will reveal a long list of definitions from various sources. The list is opened with a short definition coming from the search engine dictionary itself.

The use of photography in surveying and mapping to ascertain measurements between object.

Google.com

We also find out an interesting graph regarding the use of this term over time.

Another definition that you might encounter quite often in literature is quite the minimalist version. Looking from the point of view of someone involved with photogrammetry might seem a reasonable definition. Let’s see:

The science of making measurements from photographs. Photogrammetry means the measuring of features on a photograph.

gisresources.com

In my opinion this definition is so minimalist that can be applied to other image processing methods easily. Any image processing method is based on measuring features on photographs. Just look up on any search engine “measure features on images”. Count the times “photogrammetry” shows up. Yeap. So I wouldn’t rely on this definition when trying to explain it to someone new in the field.

Merriam-Webster online dictionary gives the origin of “photogrammetry” in 1875, and defines it as this:

The science of making reliable measurements by the use of photographs and especially aerial photographs (as in surveying)

merriam-webster.com

Again, similar with the first one but still inconclusive. This time these measurements are “reliable”. And now we see that aerial survey is involved, which of course goes hand in hand with photogrammetry. Still, in my opinion it is not enough for a good definition.

None of these definitions are wrong, obviously. Actually, experts from different fields that are using photogrammetry in their workflow are defining it as simple as they can but strongly related to their activity.

OK, you said you have your favorite definition?

Indeed. In my opinion, the best definition of photogrammetry was given by The American Society for Photogrammetry and Remote sensing (ASPRS). I use this definition in all my public talks as it describes the method in all its complexity.

The art, science, and technology of obtaining reliable information about physical objects and the environment through processes of recording, measuring and interpreting photographic images and patterns of recorded radiant electromagnetic energy and other phenomena.

ASPRS

You might find the first half of the definition used as is in many texts: ”
The art, science, and technology of obtaining reliable information about physical objects and the environment “. While this part only defines the end goal of photogrammetry, the other half contains the means and offers clues about the source data. And I believe that is quite important. Many texts refer to photogrammetry as a photography-based process.

It is true, BUT!

But the thing is that photography is usually perceived only as a visible light recording process. A complete definition of photography would be:

Photography is the science and art of creating images by recording light or other electromagnetic radiation, either electronically (sensor) or chemically (photographic film).

Spencer, D A (1973). The Focal Dictionary of Photographic Technologies. Focal Press. p. 454. ISBN 978-0133227192

Yeah, “or other electromagnetic radiation“. Of which, visible light is just a speck. I’ll elaborate.

Now let’s come back to the ASPRS’s “photogrammetry” definition.

So it IS an art, science and technology. This is important to emphasize because it reveals its depth, beauty and the skills required to be mastered.

Next, we find out what is the purpose of this art, science and technology. It is what all the other definitions have been telling us: precise measurement and interpretation of features in photographs.

Coming again to the last part of the definition, we realize that it tells us that photogrammetry is applicable on any kind of electromagnetic imagistic representation. In any spectrum. We can use it with X-Ray radiographs, multispectral imaging (multiple bandwidths) or thermal (IR) images.

I think I get it now. So why is the longest definition your favorite? Hipster much?

I wanted to explain this last aspect, especially because nowadays I often get the question: “Which is better? Photogrammetry or laser scanning?“.

And these questions are almost legit.

Almost.

Everyone knows their field and the application of both methods in their field. And they want to know whether photogrammetry is now taking the place of laser scanning. Because … everyone jumps in this ship.

I usually tell them that the answer varies with the casuistic. And this will be the topic of another interesting discussion here on my blog.

But the right question to ask would be “Which method is better for this specific case?“. Now here you can get a spot on answer. Otherwise, to a general question, a general answer without a doubt would be photogrammetry. As I said, I’ll come back and elaborate this, in another post.

So … if you do photogrammetry, what are you? Photogrammeter? Photogrammer? Photogrammeterman/woman?

You would be called “photogrammetrist“. Another word that text editor dictionaries haven’t heard about. ASPRS have a sort of definition even for this profession:

A professional who uses photogrammetric technology to extract measurements and make maps and interpret data from images.

ASPRS

It is not as complete as their definition on “photogrammetry” but it is what it is. All the definitions that I found are more or less the same as the ASPRS’s one. And it seems that the photogrametrist profession is strongly linked with geomatics, cartography, and geography. Because up until several years ago photogrammetry was a tool solely for these fields. Today it is widely used in 3D reconstruction, cultural heritage monitoring (actually since its inception) and computer vision. Perhaps some updated definitions should be required or new professions being defined.


Let me know your thoughts in the comments section below or by e-mail at laurentiu@luthonium.com . Any questions and suggestions are warmly received.

Peace,
Laurențiu

References and acknowledgments

  • The cover image was created with the Powerpoint template from www.presentationmagazine.com.
  • vintage photographs from (Jörg Albertz, 2001)
  • Literature references:
    1. Center for Photogrammetric Training (2008), History of Photogrammetry.
    2. Albertz, Joerg. 2007. A look back – 140 Years of “photogrammetry” – Some remarks on the history of photogrammetry. Photogrammetric Engineering and Remote Sensing. 73. 504-506.
    3. Grimm, A., 2007, The Origin of the Term Photogrammetry, In 51st Photogrammetric Week, Fritsch, D. (ed.), 53-60.
    4. Chris McGlone, 2013, Manual of Photogrammetry, Sixth Edition, American Society of Photogrammetry and Remote Sensing;
    5. Albertz, J., 2001. Report on the Proceedings 18th International Symposium CIPA “Albrecht Meydenbauer – pioneer of photogrammetric documentation of the cultural heritage”, Potsdam, Germany 18 – 21 Sep. 2001.

About the author

Laurentiu-Marian Angheluta

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