Our Spatial Planet

A big thank you to the organisers, delegates and exhibitors of the Mining South Australia conference who helped make Apogee’s experience at the conference more than enjoyable. While not the perfect building or layout design for a conference, the success can be measured by the response from the people who visited our booth, People were very enthusiastic about the applications for DEMs and Aerial Imagery to support their Mining Exploration project.

As key resources for Mining Explorations, Apogee exhibited a range of Digital Elevations Models. IFSAR DEMs at resolution of 5m xy posting with 50cm Z accuracy over part of South Australia, PRISM DEMs at resolution of 7.5m xy posting with 3m Z accuracy, and Aerial Imagery at resolution down to 5cm. We also demonstrated the pronounced difference between SRTM(Global DEM at 90m xy posting, 15m Z) data that is freely available.
Our 3D visualisation system NEXTIMAGE was also of interest as people could have a play and check how user-friendly and easy it is to visualise and interact with any geospatial data.

The large scale PRISM DEMs along side the dune removal technique were of particular interest to several Mining Exploration companies with interests in western and northern South Australia.

We look forward seeing the people we met again and meeting all the new people at Ausmine 2009.

According to the Scope for Improvement 2008 report from Blake Dawson, an Australian legal service and strategic business provider, released November 2008, 52% of majors infrastructure projects in 2008 were not adequately planned. A significant increase from the 42% recorded just 2 years earlier, in 2006. Even more worrying, the lack of proper scoping resulted in more than a quarter of 1$bilion+ projects having cost over-runs of more than $200 million! And we are not surprised…

In the first stage of any infrastructure project planning, surveying the terrain is one of the most important steps in order to have an accurate spatial representation of the area. The larger the project, the more critical accurate spatial data is and a significant percentage of planning time, budget and personnel should be allocated to data collection.  The Report lists three of the “Main Factors” leading to poor scoping as “Lack of experienced personnel”, “Insufficient time” and “Insufficient site information”.

This is where the appropriate use of geospatial data from aerial or satellite sensors could provide the required information. Unfortunately it is at this very important step that the biggest mistake is usually made. Because of lack of time and experienced personnel, the planning of many multi-million or even billion dollar projects are based on inadequate geospatial data in terms of resolution or accuracy, resulting in increased costs and budget over-runs. The problem maybe due to a lack of understanding or appreciation of the importance of geospatial data in providing a solid project foundation. As an example, a project may require 1m contours and in view of inadequate planning for the associated data cost, a decision is made by management to derive the contours from freely available SRTM data. Technically this is not a problem, however deriving such apparent high accuracy from the 15-20 metre vertical accuracy of SRTM at a 90m posting is not sensible. While this sounds far-fetched, this example is based on an actual project and similar extrapolation of data without due care as to the warranted level of precision is a common occurrence.

Remote sensing has been extensively used geology, mining exploration, oil, gas and pipeline planning. Recent introduction of new sensors and techniques to improve accuracy and efficiency are allowing planners to perfom virtual field trips to gather accurate information before arriving on site. From the first assessment of a project to the logistical operation, and on going monitoring, remote-sensing is an indispensable tool for all stages of any major mining project. Time and cost as well as risks can be greatly reduced through the use of Remote sensing technologies.

A range of sensors and resolutions are available for the mining industry and an accurate assessment of the most suitable data for a specific task should to be conducted to get the greatest benefit. The following list gives an overview of which data and sensors are currently used:

· Optical imagery for vegetation classification, environmental impact assessments, site rehabilitation, and operation monitoring:

o  ALOS PRISM and Spot which offer relatively large coverage with a resolution around 2.5m and very soon the Rapideye constellation with its daily coverage and 5m multispectral resolution.

o    High resolution satellites such as IKONOS, QuickBird, EROS-A/B which offer a narrow swath but 1-m and sub-metre resolution

o     Digital airborne imagery up to 5cm resolution

o    Airborne Hyper-spectral sensors with some systems collecting up to 220 bands.

Fast monitoring over a mining site

· All weather Radar data for mine subsidence, stock pile, pipeline monitoring and gold exploration:

o  TerraSAR-X, Radarsat-2, Cosmo-Skymed, for a resolution range from 100m up to 1m

o    Airborne IFSAR with sub-meter resolution (ORI from Intermap)

· Digital elevation model for planning, modelling and quantitative structural mapping:

o Spaceborne Radar interferometry data for centimetre-scale changes measurements.

o   Stereo imagery from Airborne sensors

o Stereo imagery from Spaceborne sensors such as ALOS PRISM, Spot, IKONOS, QuickBird, EROS-A/B

o   IFSAR DEM form airborne IFSAR systems such as Intermap, Fugro.

o   LiDAR

Advanced processing methodology also allows for the manipulation of basic data sets revealing features that may be of interest in geological interpretation such as the surface benath sand dunes.

ALOS PRISM DEM

Digital Elevation Model after dune removal process

All these data are usually integrated into modeling software, GIS systems and 3D-visualisation tools in addition to ground information and thus present invaluable decision level information.

Current state-of-art in commercial and research based SAR Systems.

Air-Borne Systems

Commercial - Very few purely commercial players exist in this field

1.     Intermap IFSAR - Operational X-Band single pass Interferometric System with proven track record and very large archive of proven quality data (All of USA, Europe, Britain has been mapped as well as part of Asia and Australia). Long wavelength system for foliage penetration is currently available as repeat-pass system with multi-frequency single-pass interferometric system in development.

2.     Fugro-EarthData GeoSAR - Newly operational for X-Band and P-band single pass interferometry. Available data archive is limited and data validation is not wide-spread. Theoretically should produce good quality DEM’s using P-Band but this may conflict with the X-Band results, needing reconciliation. The system is ex-NASA. The accuracy in the system is achieved by redundancy/repeat flights. A good set of samples can be obtained at the NOAA site.

3.     Orbisat InSAR - A Brazilian system with InSAR capability in X-Band and  P-band. No validation available

Research - A number of research systems exist, operated by space agencies and educational institutions. The data from these systems has limited availability and is based on research campaigns. A suitable summary is on the POLSARPRO site.

1.     AIRSAR(NASA/JPL) - The elder statesman of air-borne systems, last known campaign was in 2004.

2.     EMISAR(DCRS) - Technical University of Denmark dual-band(L/C) fully polarimetric system.

3.     ESAR(DLR) - Quad-Band(X/C/L/P) fully polarimetric system with very high quality data used for Insar, Polsar and Polinsar research. This system served as a template for the TerraSAR-X sensor.

4.     Pi-SAR(NASDA-CRL) - JAXA Airborne L-Band system, the inspiration behind JERS and ALOS-PALSAR.

5.     RAMESES/SETHI(ONERA) - Someone in France must be obsessed with Egyptian history and pharaohs, or may be it is related to the sand penetration experiments with these systems.

6.     SAR-Convair(CCRS) - Polarimetic X/C-Band system used as a test-bed for Radardat 1 and 2 sensors by the Canadians. Mainly used for ship detection research, and ocean monitoring.

Space-Borne Systems - Recent years have seen the launch of numerous SAR sensors, both civilian and military.

The following SAR satellites are those that have readily accessible data, are currently operational or will be in the near future (which can mean anytime in the next 5 years given the nature of the space industry - you can really feel the relativistic time dilation, we must be near a black hole).  Among the military ones, we can mention SARLupe-1 and 2(Germany) , YaoGan(Chinese), and many more.

Currently In-Orbit Systems - These are either old die-hard systems, long past their scheduled expiry date or recently launched top-of-the-line sensors.

1.     RADARSAT-1 - The long lived Canadian SAR system operating in C-Band HH.

2.     ENVISAT-ASAR - SAR sensor on the multi-sensor Envisat bus. The data from this sensor is accessible for research from a rolling archive over the last 15days. The sensor can operate in alternate polarization mode.

3.     ALOS-PALSAR - The first fully polarimetric L-Band space borne sensor. The data from this sensor is heavily consumed by the Kyoto and Carbon project for global forest monitoring. It collects on a fixed schedule over all land-mass. The data is highly affordable and of good quality.

4.     TerraSAR-X - Newly launched poster child of the SAR world, first commercial SAR sensor to provide up to 1m resolution. Alternate polarization mode is operational, full-polarimetry and along track interferometry are some of the research modes available.

5.     RADARSAT-2 – After long delay, it is the first fully polarimetric C-band spaceborne system and provides data to 3m resolution.

6.     Cosmo-Skymed  - 3 out of 4 satellites are currently in orbit. With a very short revisit time, this new X-band polarimetric SAR constellation is a real advantage for monitoring applications.

Planned/To-be-launched-soon systems - These are the bad boys, getting to school late or the toddlers which show great promise. Not yet in orbit but will be nice to have data from them.

1.  Sentinel-1 - Follow on to the aging ENVISAT system mentioned above, with upgrades with new technology in C-band. Unlike its predecessor, it will be a smaller and dedicated SAR bus, other optical sensors will have to find their own rides on Sentinel 2 and 3. It is due for launch in 2011

2.     TerraSAR-L(Cartwheel) and Tandem-X - The novel concept in SAR systems is a constellation, this will allow single pass along-track and cross-track interferometry.

3.     MAPSAR - An L-band joint program between INPE(Brazil) and DLR, due some time the next decade.

4.     RADARSAT Constellation - Another program due next decade or after that is designed to provide daily global coverage using SAR.

There are probably more exotic sensors, both for research and military purposes and any comments on those sensors are more than welcome.

RapidEye is a privately funded provider of satellite-derived information and services. With the release of the first public image, Earth observation is entering a new era. The  constellation of 5 identical satellites allows up to 4 million km2 to be imaged at high resolution in a daily basis.

Each satellite system can acquire data in five spectral band. It is the first commercial satellite to offer a Red-Edge band  to identify and measure unique change in the health of green vegetation.

The constellation opens up new opportunities in areas such as Agribusiness, Emergency management, Forestry, Oil & Gas, Environmental Monitoring, Defense and other markets where reliable and repetitive monitoring are required.

RapidEye Constellation

This video clip shows 36cm resolution aerial imagery draped over an IFSAR 1m z absolute accuracy Digital elevation model over Murray River, South Australia. The clip has been made with Apogee’s NEXTIMAGE.

Please wait while the video loads

In today’s world where everyone is looking for ways of improving efficiencies, Digital Elevation Models have many applications including Mining exploration, flood modelling, city planning, river and aquifer mapping, vegetation(density, height) mapping and many others in area such as road, rail, pipeline planning.

So you may be asking “What exactly is a Digital Elevation Model?”
Well, a Digital Elevation Model is a way of digitally representing the elevation at a given geographic coordinate. For every point in the DEM there are 3 values; the normal X and Y values represent the coordinates, and the Z value represents the relative height. Using these three points, we can accurately plot terrain into a visual format that makes it easier to use, while retaining the underlying data and allowing the user to extract accurate height data. The images below show 3D render of a DEM over the Coorong and part of Hindmash Island in South Australia beside a satellite image of the same area.

Coorong 50cm Z accuracy IFSAR DEM

So “Are all Digital Elevation Models the same?”
The short answer is no. There are 2 forms of DEM, DTM and DSM. DSM stands for Digital Surface Model and includes the vegetation and building elevation with the ground elevation. DTM stands for Digital Terrain Model. In a DTM the vegetation and building data have been artificially removed from the DEM to provide an elevation model of the underlying terrain.

How Digital Elevation Models are acquired?
DEM can be generated using different techniques and sensors:

• Radar Interferometry (InSAR): a SAR instrument sends microwave radiation and then record the strength and time delay of the returning signal to produce images of the ground. Elevation information can be extracted from the time delay difference between 2 SAR images over the same area. The Shuttle Radar Topography Mission (SRTM) is the most famous example of a global Digital elevation model based on space borne InSAR.  InSAR DEM can also be produced using Aerial IFSAR radar imagery to achieve better resolution and accuracy than space borne sensors. Intermap technologies provides this kind of digital elevation model worldwide.

• Aerial and Satellite photogrammetry: Two or more images are used to extract the height of any pixels on image stereo pairs utilising acquisition parameters such as focal length, principal points, platform location etc. (example ALOS PRISM DEM, SPOT DEM, EROS DEM)

• Direct coordinate acquisition: It can be achieved with surveying techniques and GPS measurement where 3 dimensional object positions are accurately determined and associated with positions on the surface the earth.

• LiDAR: LiDAR is a remote sensing mapping technique which uses a laser scanner to measure the distance between the sensor and the surfaces. Mounted on an aircraft of helicopter, millions of x,y,z positions are acquired and form a surface map. Ground LiDAR are used to measure features along profiles.

What can DEMs be used for?
When it comes to DEMs the uses are unlimited. They are essential for things such as urban planning, construction of pipelines and other infrastructure, hydrological modelling from flood prevention to tsunami predictions - remotely sensed elevation maps are invaluable to accurately map the terrain over large areas where the same data using conventional surveying methods would be prohibitively expensive. Accurate DEMs are used in flood mapping, physical modelisation,  where accuracy of the terrain mapping determines the accuracy of the resulting flood map. DEMs also have applications for precision agriculture and many other scientific and commercial areas.

Flood level using Adelaide IFSAR DEM

Interesting Related Links:
NEXTMap USA

14ARSPC Darwin Introduction drinks

Apogee staff has just returned from hot and humid Darwin where we attended the 14th Australian Remote Sensing and Photogrammetry Conference. Dennis Puniard, now CEO of the SSI, who has enjoyed a long professional career in Surveying and the Spatial Information Industry and more recently in Association Management gave a plenary session during which he pointed out that even after having had 14 such conferences, Australia still does not have any indigenous space based remote sensing capability.

14th ARSPC Darwin Conference

The conference was attended by a wide range of professionals with a large proportion from the CSIRO, Geoscience Australia and other government departments. A lot of the work presented was based on research using MODIS with people foreshadowing future intensive research on Landsat data which is soon to be made available at no cost. ALOS is another sensor used for research with various uses investigated by GA, who receive the data at no cost. PALSAR has become highly affordable through the Kyoto and Carbon project and the whole of Queensland is planned to be regularly mapped using the Fine Beam Dual polarization mode. Very few presentations were given using commercially sourced data showing the extent of reliance on free data for Australian researchers in remote sensing.

One very interesting presentation was provided by CSIRO, who are researching DTM and vegetation height extraction under contract from GA using 30m SRTM data. It was surprising to hear that GA has a copy of the 30m SRTM data as this does not seem to be publicly known, and with this data being the best national data set available, it is even more surprising that this has not been made available to the public. Why???!!!

We at Apogee are proud to present Our Spatial Planet; Apogee’s new blog about all things Spatial. With regular articles, images and videos keeping you up to date about new and interesting things happening with Aerial and Satellite Sensors.