ComputaMaps

Newsletter Volume 2, Issue 2

We've been working all year on our 3D projects and wanted to improve the way we communicate their availability to you. Our website now has a new 3D Gallery, which includes more detailed location information, images and videos of our 3D inventory. Of course, our latest projects are also highlighted in this newsletter.


View our 3D City Gallery


Our main article in this edition of our newsletter focuses on stereo photogrammetry, a key process in the creation of our 3D models. We hope it gives you a better understanding of how our products are created and why availability of recent high-resolution data and its correct interpretation is critical to our production.


We hope you enjoy this edition. As always, we welcome your feedback.

Stereo Photogrammetry –
How We Create 3D Models

 

Many end users are familiar with working with a high-resolution orthoimage as a base layer for their 3D data set so they can easily compare the model to the real world. How aerial or satellite imagery are used to create 3D terrain and building models is generally less understood. In this brief introduction we'll describe the key concepts and steps in this process – a set of mathematical principles and techniques nearly as old as photography itself called stereo photogrammetry.


At its simplest, stereo photogrammetry refers to the calculation of height values (e.g., z values) by contrasting two overlapping images. The difference in perceived location in the corresponding points in the images based on the point of view from which the image was taken is called parallax. Using the geometry based on the intersection of two rays created from their respective image's point of view, it is possible to calculate the appropriate height values for the overlapping image area.


With frame camera aerial imagery or fixed-telescope satellite imagery, the height accuracy is determined by the base-to-height ratio (B/H ratio) of the overlapping imagery (i.e., stereo pairs) collected along and between sensor flight paths. The B/H ratio is simply the distance between image collection points divided by the height of the camera, or sensor. A B/H ratio between 0.5 and 1.0 generally satisfies accurate stereo geometry.


For agile pushbroom satellite sensors such as WorldView‑1 or 2, or GeoEye‑1, we use other measurements to assess the potential accuracy of the stereo pair configuration: the angle of convergence, the angle of asymmetry and the bisector elevation angle (BIE). Of these, the angle of convergence is the most critical and describes the angle of separation between images forming a stereo pair. Stereo accuracy will be poor if the convergence angle is not between 30-60 degrees.



So how is stereo photogrammetry used in the ComputaMaps 3D production process? Once an area of interest (AOI) and product specification are established with a customer, we source the most recent and appropriate resolution data from our imagery vendors. In fact, one technical advantage that ComputaMaps has developed is the ability to search the commercial image archives for pairs of standard collection satellite imagery (i.e., single shot or "mono" imagery) that create satisfactory stereo geometry. This has enabled us to greatly increase the global archive of potential high-resolution stereo satellite imagery and thus provide high accuracy 3D data to our clients for most urban AOIs worldwide.


Once the stereo models are set up we can begin the extraction of DTM and 3D building models. For DTM generation we use a combination of automatic terrain extraction techniques using auto-correlation software as well as manual breakline editing by skilled photogrammetrists. Our 3D building models are collected using our own highly optimized 3D feature extraction software suite.


Together with clutter, linear vectors and orthoimagery, the finished DTM and 3D building models compose the essential elements of our City Planner product.

News & Events


ComputaMaps at Intergeo

 

ComputaMaps management will be attending Intergeo next month, the world’s largest event and communication platform for geodesy, geoinformation and land management. Please contact us if you will be attending and would like to set up a meeting.


3rd Symposium on Earth Observation Business


Strategic Accounts Manager Steven True will be participating in a panel discussion on location-based services on September 15 at this year’s symposium.

Recent Projects

3D projects

Bolivia

Oruro
Santa Cruz

Brazil

Brasilia
Fortaleza
Porto Alegre

Canada

Don Mills, ON
Toronto, ON
Vancouver, BC

Toronto, ON, Canada

Chile

Santiago

China

Shanghai

Shanghai, China

Croatia

Zagreb

France

Arles
Nancy
Versailles

Germany

Lichtenau
Potsdam
Weimar

Potsdam, Germany

Hungary

Debrecen
Szeged

India

Bangalore

Indonesia

Banda Aceh
Denpasar
Semarang

Japan

Nagoya
Osaka
Tokyo

Mexico

Mexico City

Principality Of Monaco

Monaco

Monaco, Principality Of Monaco

Morocco

Marrakech

Poland

Poznań

Portugal

Guimarães

Romania

Bucharest

Saudi Arabia

Madinah
Makkah

Slovakia

Košice

Slovenia

Celje
Kranj

Spain

Vigo

Thailand

Bangkok

Bangkok, Thailand

Turkey

Bursa
Izmir

UAE

Dubai

USA

Baltimore, MD

Baltimore, MD, USA


Browse our entire catalogue.

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