September 11th, 2009
Is Photogrammetry Important to the Geospatial Industry?

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Absolutely. Pho­togram­me­try is more impor­tant today than it has been at any other time. Many of the cur­rent images peo­ple see in 3D city mod­els, land use plan­ning, envi­ron­men­tal and appli­ca­tions involv­ing the deter­mi­na­tion of land­scape change are directly depen­dent upon pho­togram­met­ric prod­ucts and ser­vices. Pho­togram­mety sits at the fore­front of many 3D appli­ca­tions because it can pro­vide dig­i­tal data imme­di­ately, and pro­cess­ing tools for that infor­ma­tion are also inno­v­a­tive. Lastly, pho­togram­me­try pro­vides one of the few qual­i­ta­tive approaches for geospa­tial infor­ma­tion avail­able through stan­dard­i­s­a­tion of test­ing pro­ce­dures and specifications.

Pho­togram­me­try has come a long way since it’s ear­li­est begin­nings. That growth has been expo­nen­tial and the devel­op­ments have often rev­o­lu­tion­ary — new optics, inno­v­a­tive algo­rithms, higher speed, higher qual­ity images, for exam­ple. Many peo­ple out­side of the geospa­tial may not be aware of the size of the pho­togram­me­try sec­tor and the num­ber of peo­ple employed in it. The Inter­na­tional Soci­ety of Pho­togram­me­try and Remote Sens­ing (ISPRS) is the largest organ­i­sa­tion that rep­re­sents these indi­vid­u­als and organ­i­sa­tions. It sup­ports this work around the world in a vari­ety of ways includ­ing, edu­ca­tion, research, con­fer­ences and publications.

My first involve­ment with pho­togram­me­try began when I stud­ied forestry in north­ern Canada. It was there that I learned about stere­oscopy, cal­cu­lat­ing basic stereo photo geom­e­try and became ini­ti­ated into the process of air photo inter­pre­ta­tion. That was not an easy task for a new forester because one had to know how spe­cific tree species grew (which made for inter­est­ing learn­ing at the same time).  But it drove home the point that pho­togram­me­try was not solely about the images, but also about the inter­pre­ta­tion of those images. And that has not changed over time, although today’s dig­i­tal pro­cess­ing of images is more au­to­mated. Yet, when one talks to well expe­ri­enced pho­togram­metri­cists  today, they con­tinue to men­tion the inter­pre­tive ele­ments of the process.

We see pho­togram­me­try used in fea­ture extrac­tion appli­ca­tions today. Bound­aries can be iden­ti­fied and vec­torised, thereby mak­ing them avail­able for use in geo­graphic infor­ma­tion sys­tems (GIS). While GIS can import air­borne images as rasters, these images reach their great­est ‘value’ through digi­ti­sa­tion. Why? Because lines, points and arcs are spa­tially sig­nif­i­cant for spa­tial analy­sis within a GIS and can be used with spa­tial oper­a­tors to deter­mine rela­tion­ships to other data. That is not to say that rasters can­not be analysed spa­tially, since, they too , are geo-referenced pixel-by-pixel.  This is exhib­ited through GIS soft­ware such as IDRISI.

Upon first arriv­ing in Ger­many I wrote an arti­cle about the devel­op­ment of tri­an­gu­lated irreg­u­lar net­works (TIN). The idea behind the arti­cle was to con­struct a his­tory of the devel­op­ment of dig­i­tal ter­rain model (DTM). Not long after­ward, I received a pleas­ant note inform­ing me about the pow­ers of pho­togram­met­ric derived ter­rain mod­els. The note was signed by Dr. Fritz Ack­er­mann of the Insti­tute of Pho­togram­me­try at Stuttgart Uni­ver­sity. He kindly pointed out how the process worked and why it was impor­tant to under­stand. Later we ended up pub­lish­ing an arti­cle he pre­sented. Ack­er­mann became the Founder of INPHO — which was recently merged into Trimble.

The inte­gra­tion of pho­togram­met­ric derived images with laser based mea­sure­ments is a grow­ing field today. In prin­ci­ple, the idea is to develop high res­o­lu­tion dig­i­tal ele­va­tion mod­els (DEM) that show 3D build­ing mod­els together with the detailed textures.

Addi­tion­ally, the deriva­tion of build­ing and other heights from pho­tograme­try is related to the flight geom­e­try of the air­craft. Geospa­tially this has impor­tant impli­ca­tions where iner­tial guid­ance sys­tems, often based on GPS, are used to ensure that air­craft fly level and straight. Thus we see a com­bi­na­tion of geospa­tial tech­nolo­gies that must work together to enable the process of aer­ial pho­tog­ra­phy to take place. The cam­eras used in these processes must also then be stan­dard­ised and spec­i­fi­ca­tions made available.

The entire field of pho­togram­me­try con­sists of sev­eral cam­era man­u­fac­tur­ers. They come together using sim­i­lar test loca­tions and pro­ce­dures that enable the global com­mu­nity to under­stand, gauge and inter­pret var­i­ous aer­ial prod­ucts in a stan­dard­ised way. EuroSDR is one organ­i­sa­tion involved in devel­op­ing these pro­ce­dures and processes. This year, one of the win­ners of the Carl Pul­frich Award, Michael Cramer of Uni­ver­sity Stuttgart is highly noted for his work in this area.

The qual­ity aspect of pho­togram­me­try work is impor­tant. Attend­ing most events that include dis­cus­sion around pho­togram­me­try will invari­ably lead to a dis­cus­sion about data qual­ity issues and hard­ware spec­i­fi­ca­tions. At all times pho­togram­metrists are inter­ested in the per­for­mance of equip­ment and ensur­ing that the data pro­duced from it are quan­tifi­able and repeat­able. This has impor­tance to the inter­na­tional geospa­tial com­mu­nity. In on sense it not only builds trust between man­u­fac­tur­ers and users based on under­stand­ing, but it also sets in motion the pro­ce­dures for reach­ing inter­na­tional stan­dards and pro­cess­ing approaches from dis­parate loca­tions, resources and dif­fer­ent appli­ca­tions. This helps to build capac­ity and smooth the growth toward greater use of these tech­nolo­gies and applications.

Pho­togram­me­try appli­ca­tions excel at pro­vid­ing accu­racy down to the range of cen­time­ters. This places these devices in close agree­ment with GPS ref­er­ence net­works, mean­ing that the appli­ca­tions can be cou­pled together over wider regions.

But it would be incor­rect to assume that pho­togram­me­try only per­tains to the cam­eras them­selves. It includes all of the equip­ment and processes con­nected to the pro­duc­tion of air­borne data and derived data prod­ucts. This includes stere­o­plot­ters, image serv­ing and image pro­cess­ing etc.

Pho­togram­me­try is grow­ing in impor­tance and use. New devel­op­ments across the work flows incor­po­rat­ing pho­togram­me­try are con­tin­u­ally expand­ing oppor­tu­ni­ties for build­ing appli­ca­tions using this infor­ma­tion. There are spe­cific dis­tinc­tions between between satel­lite based imagery and pho­togram­me­try derived imagery from air­craft and UAV. Higher ada­p­ata­bil­ity, increased res­o­lu­tion, abil­ity to inte­grate with addi­tional sen­sors and time­li­ness are just a few of the advan­tages worth considering.

The role of pho­togram­me­try in the geospa­tial indus­try is at the fore­front shap­ing change, inno­va­tion and sup­port­ing higher demands for under­stand­ing plan­e­tary change.

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Jeff Thurston is edi­tor, Europe, Mid­dle East and Africa for V1 Mag­a­zine and V1 Energy Mag­a­zine. He is Co-founder of Vector1 Media.

 

Ref­er­ences

The Basics of Photogrammetry

Remote Sens­ing and Pho­togram­me­try Society

Insti­tute of Geo­desy and Pho­togram­me­try ETH

Learn­ing Dig­i­tal Photogrammetry

What is Dig­i­tal Photogrammetry

Impor­tance of Dig­i­tal Pho­togram­me­try for a Com­plete GIS

Inte­grat­ing Dig­i­tal Pho­togram­me­try and Ter­res­trial Laser Scanning

EuroSDR — Pho­togram­me­try Related Research

Pho­togram­met­ric Data Cap­ture and the Cre­ation of 3D City Models