OPERATIONAL ENVIRONMENTAL SATELLITE DATA APPLICATIONS:

HOW THE EOC CAN HELP ACHIEVE THEM IN AUSTRALIA.

David L B Jupp

CSIRO EOC Science Leader

April 1997

1. ENVIRONMENTAL SATELLITE DATA APPLICATIONS

Environmental Satellite Data have provided the promise of monitoring at regional to global scales for more than 15 years. The data time series has been growing since the late 1970's first as the NOAA TIROS and later as the AVHRR data series. In recent times, the NOAA 'Pathfinder' data sets have provided a pointer to maturing Standards of processing and products.

The data provide regional to global scale information for environmental monitoring, they have high time resolution and can be acquired and processed for low cost per sq km. The products have stabilised and have many applications.

Examples of environmental management & monitoring which are now heavily dependent on AVHRR data include:

The Environmental Satellite data scale is right for this wide range of applications. Valuable and immediately useable products are available commercially and the cost frame is acceptable for a well defined set of applications.

Despite this "undeniable opportunity", there is still user resistance to the widespread operational use of AVHRR based products in Australia. I believe the problems stem from lack of consistent and accepted user experience with data delivery, quality and interpretability. This is despite years of extensive international and Australian R&D.

2. KEY ISSUES IN ENVIRONMENTAL SATELLITE DATA APPLICATIONS

The Key Issues can be separated into questions of:

What is Necessary for effective operational use?

What is Possible for the best quality operational use?

Over the years during which high quality R&D has occurred internationally and in Australia, "what is possible" has been discussed more than "what is necessary". Yet it is "what is necessary" that is the basis for the market and operational use of these data. Briefly, we can state:

Despite considerable work, consistent and standardised data sets have not been produced. Users and suppliers have been forced to use empirical standardisation to overcome obvious variations in the data which are not due to changes in the earth surface properties. Such empirical and data dependent approaches are not satisfactory for truly operational applications.

In addition, despite research throughout the world, it seems difficult to establish an acceptable standard set of advanced scientific algorithms or an accepted "best practice". However, for end users and for a market to be established and sustained it is essential that effective standards for both base products and algorithms become agreed and standardised.

3. CURRENT BARRIERS TO OPERATIONAL MONITORING

What are the most significant Barriers to successful operational use of these products in Environmental Monitoring, Assessment & Measurement? What must we do to achieve "what is necessary"?

The barriers are in three primary areas:

1. Data Access & Communications

The large amounts of data collected over 15 years are dispersed into many different holdings, with varying levels of processing and with variable levels of accessibility.

2. Data & Product Calibration & Performance

A minimal requirement for monitoring is a level of consistent and well defined calibration. Ideally, if there are no changes to the signal reaching the sensor, the base products should not change. Approaches to data calibration are variable with data suppliers often forced to accept empirical standardisation and there are few attempts to assess the accuracy of base products. In addition, to compare information over time at a given location requires accurate geolocation or navigation of the data. To separate earth surface changes from those of the atmosphere minimally requires pixel cloudiness to be flagged. These basic requirements are not being met with consistent and (in many cases) acceptable accuracy for user's needs.

3. Data & Product Consistency & Standardisation

Many groups, as well as station operators and commercial groups provide value added products such as Sea Surface Temperature (SST) and Normalised Difference Vegetation index (NDVI). However, the algorithms used vary, are often not documented precisely, are sometimes not able to be re-processed if changes to (say) calibrations become available and are rarely validated operationally.

4. CSIRO EOC TASKS ADDRESSING THESE ISSUES

Since CSIRO has collected, researched and used AVHRR data for much of the past 15 years it is important to ask "What is CSIRO (EOC) doing about this situation?"

The CSIRO Earth Observation Centre (EOC) (COSSA, 1996) has been set up in response to some of these issues as they occur in the wider field of earth observation. Its catalyst was the Simpson Report (Simpson et al., 1995) which dealt specifically with data issues of the kind outlined above. It pointed to a level of generic fragmentation in the CSIRO effort as a factor in preventing some of these issues being addressed. With an EOC in place to overcome this fragmentation, what is being done?

Among EOC Task activity for 1996/97 (see Jupp, 1997 for more detail) are the following:

1. ILS, IMS, IDN & LAS at Canberra for the Global 1km data system

As part of the USGS global 1 km data project, AVHRR data from the stations covering our region (Perth, Darwin, Townsville, [some Melbourne], Hobart, Casey and some from Manila) have been collected in a data archive at the EOC in Canberra. The data series is complete for the Australian land mass and covers from 1992 to present. The management of such data is being demonstrated by its linkages to the world via

The purpose of these demonstrations is to develop a capacity for the EOC to guarantee data access to researchers when no other option exists and to undertake comparative data management studies that will enable the best common approach to data management to be established for CSIRO and other Australian data managers.

2. AVHRR Calibration Web Site

Base calibration for AVHRR data is an important issue. The EOC is tackling the problem by setting up a Web site (CalWatch, http://www.eoc.csiro.au) that records the current best estimates over time of calibrations for different sensors. If possible, it will record the actual or likely calibrations used by some of the more common data suppliers so that the data users can judge the effects for their applications. This work is being done collaboratively with the Canadian CCRS. Task leader is Ross Mitchell of DAR who is working with David Parkin of Canberra EOC to maintain the Web site facility.

3. Station vs Time Series Strategies for Calibration

A station operator or near real-time data producer must choose calibrations without current or future knowledge of sensor operation and performance. Past data can benefit from information from the invariant sites of the type described below. Choices of the best strategy for near real-time calibration are being studied to minimise the problems this can create. This involves current calibration estimates and the history of calibration change for a specific satellite and instrument. It is especially important for near real-time uses.

4. Cal/Val sites for product and methods testing

A range of sites have been or are being instrumented for calibration monitoring, atmospheric property measurement and validation of products (referred to generally as "Cal/Val"). These are the CIGSN network (Hay and Amburla) managed by Fred Prata of DAR and a new desert site in northern SA (Tinga Tingana) being instrumented by Ross Mitchell and Denis O'Brien of DAR and Dean Graetz of Canberra EOC with permanent sun photometers and other instruments. These sites provide a base for quality testing as well as calibration monitoring and validation missions. The EOC is investigating how to maximise the consistency and standardisation of field and validation mission data by forming a shared instrument resource, establishing the location and status of instruments at Divisional sites and the examining current status of measurement protocols in well established missions. This is being done through a specific instrumentation Task by David Parkin of Canberra EOC and Bob Cechet of DAR.

6. CAPS for Navigation, Calibration & Cloud Tagging

The algorithms developed at CSIRO Division of Atmospheric Research and Marine Labs are of high quality and can provide a common basis for Australian base and advanced products. The best choices for Navigation, Geolocation & Remapping, for Calibration and for high quality Cloud Tagging are being realised as an open and extendable software suite called CAPS (Common AVHRR Processing System, Prata (1996)). CAPS is a joint effort between CSIRO Mathematical and Information Sciences, Marine Division and Atmospheric Research and will provide a level of algorithm description as well as coded demonstration that will enable it to be used as it is or provide a blue-print for best practice code development.

5. CURRENT OPTIONS FOR ADVANCED HIGH QUALITY PRODUCTS

The above discussion was about what is necessary for the Environmental Satellite Data Series to realise its promise among users. It is only when these primary issues are addressed that the full view of what is possible can be had. What is possible in monitoring is to separate real changes in the earth's surface condition from those only in the data and to derive geophysical parameters from the measurements the data provide for those changes. Technically, this involves:

What is the CSIRO EOC doing in this area? Current EOC Tasks addressing these opportunities are (Jupp, 1997):

1. CAPS

CAPS as outlined above is being defined as a base system in which to document and implement these advanced processing methods. It is a software environment but it is not an image processing system. It is being developed as a tool kit that allows users to work in most image processing environments.

2. AtCor studies using CalVal sites

The Calibration and Validation site network, as well as providing a means to quality check base products, is the source of information for atmospheric correction (AtCor) studies. These are being related to water vapour and aerosol climatology's (best default choices) and provide test data for comparing methods. Atmospheric correction is a major factor in retrieving data series that are primarily responding to surface effects rather than instrument, sensor view or atmospheric effects. However, it is still a scientific research area and uninformed use of atmospheric correction can make data series less standardised and consistent.

3. Scene Brightness

The surface effects such as BRDF (Bi-directional Reflectance Distribution Function) and BEDF (Bi-directional Emission Distribution Function) can all be looked at as varying scene brightness that does not indicate changes in the surface type and condition but rather the varying sun and view geometry of the data. AVHRR and airborne data both share the problems of widely varying scene brightness. AVHRR in particular must account for these effects. Canadian researchers have indicated about 30% of the variation in AVHRR based NDVI can be due to sun and view angle effects. No wonder deserts can 'green' in the winter! The EOC has a specific Task which is tackling BRDF and varying atmospheric effects at a range of scales and which aims to define a BRDF 'typology' for Australian landscapes that can be used to correct Environmental Satellite Data for these effects. The potential to effectively combine calibration, atmospheric correction and scene brightness corrections to create a standard base data set is one of the major goals of the EOC.

4. Best Practice Demonstrations

The end-to-end combination of data management, base processing, advanced information extraction and data series production is being demonstrated in time series of AVHRR, GMS and Landsat data. In the case of AVHRR data, a collation of the current CSIRO best practice is being supported in the Data Consistency & Standardisation Thread. This, and similar demonstrations, aim to provide demonstrations of what is possible based on best practice in what is necessary and best current choices of CSIRO advanced algorithms.

6. BRINGING IT TOGETHER

The EOC and its "Earth_Observing_Crew" in CSIRO can take actions but they will not develop and expand the market for operational use of Environmental Satellite Data unless the actions are coordinated with user needs and supplier needs. We need to consider the options for a nationally consistent effort on product consistency and standardisation in (minimally) AVHRR data. This will be a framework that can be applied to other satellite data but in the immediate future it has a special need for action.

The main groups that need to discuss this issue are CSIRO (through the EOC), the Bureau of Meteorology, QDPI, WASTAC, AIMS, ACRES and representatives of the small but significant user community. There have already been important meetings and discussions concerning these issues (McVicar, 1996; Jupp, 1996).

Principles we must keep in the forefront are that by coming to agreed approaches and standards at the base product and supplier level we are investing in product quality to build the whole market. It is against everybody's interest for the current situation of product inconsistency and lack of standardisation to continue. It is in everyone's interest for the base product issues to become non-issues. The real markets and benefits are in the value added products. At present, the impact of these is being compromised by the varying quality and standards among the data archives and supplies across Australia and the differences between these and the data available via the internet from the US.

The CSIRO EOC is investing in Data Consistency & Standardisation because of its underpinning effects on all products. However, the EOC is science focussed and its primary aims are to develop the improvements in the "What is possible" area. If a concerted effort can be brought about, it would be possible for some of the current EOC Tasks to move from a research time frame to an operational time frame. These include the Calibration studies, CAPS and the [data series]. This move will need support of various kinds including collaboration of staff from the different organisations and some specific funds to focus Tasks and bring their outcomes into the required time line of the Australian product suppliers and users.

Some steps to starting these discussions have occurred but they are not enough. It is time for the parties, with the pressure and support of the user community to nail the issues and see environmental Satellite Data realise its "Undeniable Opportunity".

REFERENCES

[EOC Web Site: http://www.eoc.csiro.au/eoc/eoc.htm]

COSSA (1996). CSIRO Earth Observation Centre Strategic Science Plan. Vision, Mission and Strategies 1996-2000. (EOC Web Site)

Jupp, D.L.B. (1996). Land AVHRR Data Users Group Workshop - Towards Product Standards, ARSC8, Canberra. (EOC Web Site)

Jupp, D.L.B. (1997). EOC primary Tasks and forward looking Working Groups for 1996/97. (EOC Web Site).

McVicar, T. (1996). Land AVHRR Workshop, ARSC8, Canberra, Monday 25th March 1996. Meeting Report. (EOC Web Site).

Prata, A.J. (1996). Working Group on Australian AVHRR Science. Final Report: Recommendations and Proposal for a Common AVHRR-data Processing Scheme - CAPS. Revised April 1996.

Simpson, J.J., Barton, I.J., Kingwell, J., Neal, A.B. and Wallace, J. (1995). Review of CSIRO Multi-Divisional Program on satellite data acquisition and utilisation (MDP-19)/ Analysis of CSIRO Earth Observation needs., COSSA Publication 34, May 1995.


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