Thoughts from Geo-12 (day2)

As the title suggests, I was only able to attend the second day of this years Geo-12 event. However, the talks I did see where of excellent standard and I will hopefully communicate some of the key ideas here. The talks where titled:

1. 3D Laser Mapping – Mapping vs Survey Grade by Andrew Fuller
2.  Ten things not to do with maps by Mary Spence
3. Everyone can be a hydrographic surveyor by Tim Thornton

The 3D Laser Mapping talk though not my main focus proved to be very informative and highlighted the development of terrestrial laser scanning. The first point was that survey grade accuracy is typically <3cm whereas mapping grade is <100cm. The talk also reiterated the importance of mission planning when conducting high accuracy surveying. Due to the varying positions of the different positing systems during the day it is important to conduct a survey when the greatest  number of satellites are overhead. This is even more important when working in urban canyons where aerial visibility is severely limited.

Andrew Fuller talked in some detail about the use of Inertia Monitoring Units IMU which work to correct position whilst allowing the scanner to know its position even when satellite coverage is inconsistent. To see the results of the surveys have a look at the video below. It is quite easy to see how this could be transferred into the games industry to create real world places.

The next talk was one with a balance of humour and purpose. Mary Spence gave a rapid and well illustrated sample of common cartographic mistakes and possible solutions. Her talk worked through the most common ailments including colour, labelling map furniture etc highlighting correct vs incorrect use.

As was highlighted, many of the suggestions made where common sense however, commonly forgotten. I will give a few examples of Mary’s recommendations below.

1. Map Content

The final point of Mary’s talk was on the subject of map content. All too often a cartographer seeks to embed far more information onto a map than is required and will typically lead to congestion and confusion. Mary highlights the importance of planning and the consideration of output type and size, purpose and user. She used the example of one customer who used the phrase “It seems a shame not to include it” having digitised more data than required.

2. Marginalia

Again a common mistake with map makers is the use of text such as “Map of….”, “Legend showing..” and “This map contains…”. In the majority of cases these statements are redundant and remove the professional impression of the map. If it requires the designer to tell the reader it is a map surely it is not a very good map. Additionally when a designer uses arty borders, north arrows (a topic of their own) and insets then the question must be asked is the designer trying to hide something about the actual maps quality.

3: Do not lie

This line was shown alongside the Kingston university 3D campus map which the university paid a large amount of money to complete. The project included the use of helicopter surveys yet the final product is over generalised and as such is a very poor abstraction of reality. This was one of the motivations of my past lecturer Dr Ken Field to get students to create a more appropriate map.

The final talk Everyone can be a hydrographic surveyor by Tim Thornton was possibly one of the most significant. Tim Thornton presented the work of TeamSurv, an open-source bathymetric mapping project. The project aims to collect large amounts of depth data from yachts and cruisers and to collate and map the data. The project appears to be well engineered and takes into account many of the questions regarding data quality that may be asked. Firstly, all data submitted is collated into a database and a certain density of recordings is required before a depth is placed on the map. Through the use of regression analysis all depths may be plotted and those which are beyond a sensible range are excluded. User who regularly submit  poor data are blacklisted or asked to recalibrate equipment. The next portion of the project is the correction due to tidal heights and sea temperature. The project takes into account sea temperature on the speed of sound/light in water and uses almanac data verified alongside live tide sensors to make all results consistent.

The majority of data collection to date has taken place within the Solent, however as the project grows they are now collecting data on a global scale. In addition the project has had some of their results in the Solent verified through wide beam sonar bathymetric scans. These professional surveys suggest the TeamSurv data is correct to +- 10cm. Coverage within the Solent is now good however, there are a number of blank spots at shallow regions.

I think this project is very interesting and is certainly one to follow. As the project expands and more users contribute it will be interesting to see strategies designed to increase coverage and infill certain parts of the dataset.



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