Mexico City –
A City Planner Case Study
ComputaMaps' rapidly expanding catalogue of City Planner products is largely driven by customer demand.
During 2010, a customer deploying a secure radio system in Mexico City approached ComputaMaps regarding the production of a City Planner database.
The area of interest (AOI) covered an impressive 1600 square kilometers, with more than half consisting of dense urban settlement.
While Mexico City isn’t the largest City Planner data set we’ve produced, the world's eighth largest city certainly ranks in our top ten.
For this reason, we believe it makes an interesting case study to showcase our 3D capabilities.
The work flow for producing our City Planner product generally consists of the following steps:
selection and procurement of suitable high-resolution satellite imagery (in this case 50cm) for the AOI;
image processing and stereo-model setup;
building geometry and terrain model compilation;
product quality assessments and control;
and finally, delivery of a product that meets the customer requirements and expectations.
Covering the AOI required 14 separate and overlapping stereo pairs.
Additional GPS ground control was used to increase the absolute xyz accuracy of the extracted data.
The Mexico City database contains a staggering 2.9 million building polygons.
Each building was extracted using photogrammetric principles
Stereo Photogrammetry – How we create 3D models)
to calculate the height values from a stereo-image pair.
From each perspective image view, the geometry from the intersection of two rays
(for the same building point) is used to compute accurate height values.
In some instances, multiple polygons would be captured to define a single building.
This process was completed for each and every building within the project area.
The resultant building geometry (x,y,z), provides an accurate 3D digital model of the city.
Once the production phases were completed,
the data layers were run through a series of quality assurance and control checks.
The assessment analyzed the various product deliverable layers and identified any potential inconsistencies
between geometry of adjacent polygons, building heights, missing or incorrectly placed buildings and the intersection
of transportation vectors with building polygons.
As with all projects, this phase is critical as the product must be successfully loaded into an
RF Planning tool and provide a complete and accurate city model on which to perform radio propagation studies.
We have since received positive feedback regarding the product quality and accuracy,
which included extensive post-delivery acceptance testing.
The entire project was completed in approximately 50 business days from order to delivery,
and was produced in parallel with many other projects.