One thing that is often difficult to convey in your everyday life is just how much technology has changed over the years. Not only are people more mobile than ever, meaning it’s more important for us to have access to information wherever we go, but there are all kinds of ways of getting this data too!
The first step towards mobile mapping was satellite imagery, which became so advanced by the 1980s that you could buy individual photos at incredibly high resolutions (if you were rich enough). The next innovation was lidar surveys, using lasers instead of satellites to get geographical data – but lidar didn’t become something that could be used by non-experts until lidar scanners came along. This whole process went into overdrive when GPS systems became small enough to fit on mobile phones.
Mobile lidar scanners can be fitted onto any vehicle, but they work best on things like quad bikes and maybe helicopters. The lidar scanner rotates as it moves along, sending laser beams out in all directions at the speed of light (roughly 186 thousand kilometres per second). The lidar scanner “sees” objects by measuring how long it takes for the lidar beam to bounce back off them; the lidar data is stored onboard until you return to where you started, at which point you upload it all to your computer.
The lidar map above shows a city centre with just three lidar scans – note that each individual scan only covers a small area! This would have taken about an hour to complete, lidar mapping has come a long way since lidar scanners were first used in the 1980s.
Once you have your lidar data, you can use GIS software to turn it into something useful. The lidar map above was taken from Google Earth – note how much more accurate this looks than an aerial photo! Lidar maps are also good for showing what’s under the ground – lidar maps of ancient cities bring them back to life by showing just where some of the roads were.
Mobile lidar scanners are still pretty expensive, but they’re getting cheaper all the time. A few years ago they cost around $1000000 each; now smaller ones can be had for less than $1000,00. That’s still pretty pricey, but lidar scanners aren’t like mobile phones – you can keep them for years and they don’t break down.
Lidar mapping is just one kind of mobile mapping system (or MMS), there are plenty more out there. Some use lidar scanners, some don’t; all take readings in many places at once to give a complete picture. They’re useful because you can get the data wherever you go, rather than having to map out an entire country or world by hand! Once your field data has been mapped digitally – either with lidar or another technology – it becomes much easier to find new things too! That’s why it’s so important to be able to keep up with technology if you want to go into the exciting field of mapping.
So lidar scanners give highly accurate lidar data, which can be used to make either point clouds or digital elevation models (DEM). Point clouds are more useful for 3D visualization and alteration, while DEMs are better for detailed contour plotting and working with elevation slope. Both lidar scans and MMS require a lot of testing to understand how they work properly, but lidar is far more accurate than MMS since it provides exact measurements rather than an estimation. A lidar survey usually takes between one to two hours depending on the terrain. A MMS on the other hand uses multi-spectral bands such as infrared and visual light to capture the landscape.
Once lidar data has been taken, it is then used to create a lidar map – either in 2D or 3D formats. The lidar map would then be combined with road maps and satellite imagery to provide a user with a location-based service (LBS). Location-based services find a person’s location by using the Global Positioning System (GPS) network of satellites orbiting Earth at about 20 000 km above the surface. MMS can also be used for proximity searches such as focusing on something close by even if you don’t know exactly where it is. This information can be presented on mobile devices such as mobile phones and personal navigation assistants (PNDs), providing users with accurate directions and other location-specific data.
The lidar map above shows the lidar data in 2D format, but lidar mapping software can also be used to visualize lidar data as 3D models (seen below). MMS is useful for collecting field data during operations because it provides an abundance of information for analysis without requiring extensive efforts or time. A scanner can gather up to 1 000 000 points per second which means that a 10 minute flight would result in roughly 350 000 000 measurements! This makes it easy to see what’s around you at any given time which also comes in handy when planning a lidar survey. Some lidar scanners even have thermal imaging cameras built into them, allowing users to collect both lidar and thermal images at the same time and in one system. This lidar survey shows the lidar data in 2D format – compare that to the lidar data at the top of this article which is 3D!
Lidar technology is an important tool for collecting lidar maps and lidar scans, but it’s not always needed when mapping out geographical locations. The only lidars currently available are expensive and large, so they aren’t yet practical for everyday use by small businesses or environmental consultants. MMS however can be used anywhere and provides a multitude of benefits even if lidars aren’t used.