ADF Weapons Project: 3D mapping for artillery | ADM July 2011

Gregor Ferguson | Sydney

Saab Bofors Dynamics has developed a solution to a persistent fire support challenge – ensuring both precision and accuracy. Field artillery has always been effective against area targets and properly identified point targets. The emergence of Precision-Guided Munitions (PGM) such as the 155mm Excalibur round has also enabled artillery to deliver pinpoint terminal effects to a specific geographic coordinate. The same technology enables GPS-guided weapons such as JDAM and the Small-Diameter Bomb (SDB).

However, in order to get maximum value out of a PGM the target must be located accurately and precisely. This might be problematic during a mission, especially if the distance between the target and the Forward Observer (FO) is more than, say, 3km or if there is no clear line of sight for a Laser Range Finder (LRF). Under these conditions the target position reported by the FO could be inaccurate by several tens of metres.  A Target Location Error (TLE) of, say, 50m will reduce the effect of a PGM engagement considerably – you’ll miss the target, though with very high precision, and may cause unwelcome collateral damage or friendly force casualties. 

Rapid 3D Mapping

This problem is well known among operators of PGM. The accuracy of a target observation platform depends on the quality of its gyros and LRF as well as the operator’s proficiency. All these elements contribute to the TLE, which will increase with the target’s range from the FO. It’s possible to help the FO by providing him with an improved target observation platform with better gyros and/or LRF, but there will always be a practical limit to what can be achieved, according to Michael Olofsson, of Saab Bofors Dynamics.

A Rapid 3D Mapping™ system developed by Saab Bofors Dynamics reduces the TLE significantly as the FO can pinpoint the target directly on a detailed 3D map displayed on a hand-held Artillery Target Viewer – this can be a simple ruggedised laptop computer.

Rapid 3D Mapping is a method where photos of an area taken from different angles are compiled into a very detailed, accurate 3-dimensional picture (a 3D Map) generated using high-speed, sophisticated algorithms developed by Saab Bofors Dynamics.

This 3D Map is presented on a viewing screen and the FO simply correlates the image on the screen with his real-world view, and then marks the position on the screen. This reduces the TLE markedly and field trials have shown that it is an easy correlation to perform manually. 

To illustrate how it works, the above image shows the real world view from an FO’s position.  His task is to define the coordinates of centre of the STATOIL storage tank. The target is about 3 km away.

Even if the FO has unbroken line of sight he can’t be certain the LRF beam is being reflected from the roof of the storage tank. If he aims the LRF at the wall of the tank in order to be sure he’s hitting the right one, he must recalculate the target location coordinates in order to locate accurately the centre of the tank. 

However, access to a 3D map of the area improves the target location process radically. The smaller shows a screen dump from the Artillery Target Viewer showing a 3D map over the target area. It should be noted this is not an oblique aerial photograph: it is a composite image made up from several photos taken from different angles and elevations, georeferenced and fused into a single 3D Map.

In the upper left corner there are three information lines:

Observer Position: This displays the FO’s exact position. This information is fed into the Artillery Target Viewer by connecting a GPS receiver, by manually marking the 3D Map with a mouse click, or by typing it in manually. The FO can verify his own location by panning the viewer to show a blue circle indicating his own position – he can adjust this if necessary.

Target Position: This line gives the target coordinates. The red circle on the top of the oil storage tank is the target position. The FO can place the red circle on the target by using a target observation platform like the German NYXUS or the Swedish EOI, and operate it in the normal way.

The target position calculated by the instrument is fed directly into the Artillery Target Viewer and the red circle appears. The FO can use his mouse or track pad to adjust the position of the red circle and drag to the selected point of impact. When the circle is moved the target coordinates are automatically updated. The target is now pinpointed and the coordinates can be fed into the fire control network.

The FO can also place the circle on the target manually once he has positively identified the target position. This manual process doesn’t require a target observation instrument. All the FO needs are a ruggedized tablet computer, compass and binoculars. This method also enables other personnel than the FO to define coordinates of interest which he can then enter. 

Bearing and Distance: This line gives the actual bearing and distance between the observer location and the red circle.

Saab Bofors Dynamics developed the Rapid 3D Mapping process using its expertise in image processing and navigation technologies. A combination of these two technologies makes it possible to create highly accurate 3D maps of a selected area very rapidly. The positional accuracy of an element in the Rapid 3D Mapping data is better than 0.5 metres georeferenced in longitude, latitude and height. The pixel resolution is about 10 cm, depending on the registration altitude and camera resolution. Almost any kind of airborne imagery (including satellite and FLIR imagery collected from a UAV) can be used to create the 3D Map, says Olofsson – the higher the resolution the better, of course.

The registration utilizes differential GPS which is common in most countries and the correction signal is distributed by several providers. If the differential GPS is not available from a provider a ground station has to be used during the registration.

The next step after registration is the generation of the 3D maps. The Saab Bofors process generates 3D maps of the same resolution as High Definition TV almost instantaneously. These can be viewed in a viewer and exported to a geospatial information system. The export interface against other existing software/programs is adapted to fit most of them.

Much depends on the image resolution, says Olofsson, but an HDTV-quality image of can be processed in real time, which means reaction time in the sensor-shooter link is kept short, while mission preparation can be carried out at relatively short notice.

The product is already operational in the commercial market: more than 50 cities around the world have been modelled as 3D maps. The Artillery Target Viewer application is a prototype at present but virtually production ready, according to Olofsson.

The advantage of such a Rapid 3D Mapping system isn’t so much its contribution to weapon precision:  GPS guided artillery shells, rockets and bombs are already extremely precise weapons. The system enables the FO and force commanders to locate targets very accurately and precisely in order to deliver maximum effect as well as satisfy stringent rules of engagement and minimise the likelihood of collateral damage or casualties to friendly forces.

Subject: Simulation