CadastreGoogle earth / mapsLeisure / inspiration

Can I use Google Earth images for the cadastre?

After a moment of good humor with a Dutch friend today, I rescued some similarity between the process that leads cancer in clinical psychology and the Google Earth romance with the wrong ends:

Stage 1: Scare.

A technician goes to the field in response to a measurement request from an owner who wants to sell; check that there are new buildings that are not visible on the cadastral map. Then he comes to the office and sees that the orthophoto from 40 years ago only shows vineyards on that periphery, with a large plot in rustic conditions.

Call the technician who has been there for 23 years, growing old with a stereoscope around his neck and a worn leroy that only makes letter letters; After struggling to superimpose one layer on top of the other, they identify that in effect, on the map there is just what is in the image.

So they decide to resort to the novelty of the last year; Google Earth has arrived the year 2004 and shows a colorful orthophoto where the recent buildings appear.

Then comes the scare: The coordinates of that plot do not coincide with those of the map, they are more than 20 meters out of date.

-Be careful-. It tells you the quaternary. -These coordinates were made by ancestral aliens, and only they can change them.

Aware that Google cannot be that wrong, it moves its entire cadastral layer to match the image. Then he calls his superior and impresses him by showing the digital terrain model that matches the cadastral layer that he has exported to Google Earth.

Excited with the novelty, the head of the ejido commission asks him to issue plans for each property, to sell all the neighbors at a better price "certifications of plots matching Google Earth"... and now in WGS84!... SEO optimized!

Stage 2: Denial

Two years later Google appears with an image that says 2006; The technician assumes that the image is more recent, he realizes that the location of the building is almost 6 meters displaced to the south east of where he moved the polygon, now drawn in green.
You find it surprising that now the coordinates of the maps you have printed are not right with either the original maps or the new Google image. By then the hand-drawn maps are abandoned in a bathroom that became a warehouse since the day the Quaternary was fired.

Your fear turns into denial, because you can't accept that Google is wrong; not this time. So it leaves the property in question and the entire city where it was moved; waiting for the problem to resolve itself.
It still decides to issue the new certifications based on the new coordinates, with a displacement rounded to 6 meters.

Stage 3: Acceptance

Three years later Google appears with a new image of 2009, and as you can see, the detail is much clearer.
Notice that the building was not the way it had been interpreted.
It coincides with the location of the last year, so it ends up accepting that its parcels are 6 meters displaced .. so it decides to issue other certifications with the displacement, although this time without rounding.
It is surprising that the image has the new building constructed in front of the plot, reason why it arrives at the conclusion that there can not be more precise information; so that it moves all of its 6.47 meters cartography at an inclined angle of -27 degrees.

The quaternary old man goes through the office for a sales purchase procedure and is scared to see that the coordinates are strange. He tries to make suggestions or look for the origin but gives up after being shown some themed shapes based on the construction typology.

Stage 4: Death

He decides to wait one more year, to 2010 and goes to field to make the appraisal of the building whose new building is in the image. Of step to release some wonderful equipment whose publicity is not paid to make mention ... 19 centimeters of precision, without postprocess.
Place the GPS and see that the coordinate is displaced, does another test of 15 and 25 minutes and the coordinate confirms that it is ... quite displaced. Leave the GPS taking a longer reading while waving for a long time to the new owner of the property in front; This invites you to have a coffee in the corridor overlooking the GPS that cooks in the midday sun for almost 40 minutes.
The neighbor replies that he has bought the property three years ago, and that he has already registered it in the Property Registry, which now requires plans with precise coordinates. UTM WGS84… SEO optimized!
With some fear and desire to pee, he asks for the document of the property and this one removes it of the doubts:
He has gone to register the plan with the building certification that he has given to the commission of Ejidos in 2007; And he said thank you for having made the update because now you are sure that the demand that two neighbors have put you will not have justification because it has a recent plan while theirs is more than 30 years.
Take measurements over, over, over and over again. Get a more precise device, and finally ends up convinced of reality:
-The measures of the Google estate are offset 23.87 meters!

Golgi Alvarez

Writer, researcher, specialist in Land Management Models. He has participated in the conceptualization and implementation of models such as: National Property Administration System SINAP in Honduras, Management Model of Joint Municipalities in Honduras, Integrated Cadastre-Registry Management Model in Nicaragua, Territory Administration System SAT in Colombia . Editor of the Geofumadas knowledge blog since 2007 and creator of the AulaGEO Academy that includes more than 100 courses on GIS - CAD - BIM - Digital Twins topics.

Related Articles

3 Comments

  1. Care must be taken when using a geographic data source that was not designed for that purpose, especially to support the cadastre, unfortunately Google Earth presents a cluster of satellite images with little rigor in the post processing, that makes the images present some displacement if we compare it with another one from a different year.

Leave a comment

Your email address will not be published. Required fields are marked with *

Back to top button