Abstract

The ability to exchange Digital Geographic Information (DGI) is fundamental to the interoperability of military Command, Control and Information Systems (CCIS), both at the national (joint service) level and at the international (combined forces) level of co-operation. The paper will outline how military standardisation guides the portrayal and information content of the digital products, with the needs of inter-service interoperability driving the common format of the data to the use of the geographical reference (Lat/Long) and the ARC projection. Within the NATO alliance, the standardisation and exchange of data, between producing nations, is achieved through STANAG 7074, the military implementation of the DIGEST standard. The paper will outline the recent developments that have culminated in the promulgation of the revised DIGEST v2.0, together with the associated developments in the UK Military Standard Products for DGI, such as the draft Image Map product, which uses GeoTIFF. The increasing use of Standard Military Products, within CCIS, has given rise to significant challenges in the management and selection of geographic information. To conclude, the continuing improvements and enhancements to the UK Army TACISYS capabilities will be summarised.

INTRODUCTION

1. The underlying imperative of an effective Military Command, Control and Information System (CCIS) is to be able to cross relate all the military information on "what" and "when" to the geospatial reference of "where". A "closed" military CCIS, such as a single Battle Group Management System, will need to be consistent in its interpretation and portrayal of the underlying geospatial reference, so that the database features, such as unit locations and inter-unit boundaries, can be accurately displayed on a screen projected map. However, if the dissemination of the Battle Group information is not shared by any other system(s), as long as the geographic reference system is consistent, the underlying geographic information and the associated manipulation by the GIS can be optimised (or constrained) by the system design, to deliver to a unique specification. However, such "closed" systems are increasingly rarer, as the development of Military CCIS is being driven by the common requirements of efficiency, economy and standardisation essential for digitisation of the battlespace.

GEOGRAPHIC REFERENCE

2. With the greater emphasis now being put on Joint Service operations in the recent UK Strategic Defence Review, together with the recent British Defence Forces’ experience of NATO and other international alliance joint and combined operations, the ability to exchange geographic position and information, in a common reference system and format, has become increasingly important. If military information is to be used by different systems, either within a single nation’s navy, army and airforce, or across nations, the fundamental interoperability of the underlying geospatial reference and information format cannot be taken for granted. The one common denominator, that underpins the GIS environment is the geographic position. All geographic position references are related back to the true ground position, through the mathematical relationships of grids and datums. This relationship of grids and datums to the "real world" has undergone a fundamental review with the advent of the Global Positioning System (GPS) for which a new "geocentric" reference system was developed, known as WGS84. Prior to the introduction of WGS, the proliferation of local grids and datums, originally developed to "best fit" a national survey to the earth’s surface, had been subjected to review and adjustment, the most relevant military development being the adoption by NATO of ED50 over the ACE operational area. To re-cap on part of my presentation from last year with the example, on my own experience with the UN in the Former Yugoslavia, might put it into perspective. The mis-match of datums in the Former Yugoslavia is demonstrably at its worst, but no means unique. The 1/100,000 scale maps used by the UN were a modern WGS 84 product, which could be used by the UN forces to call in a NATO air strike. However, the original NATO maps at the time, were a Cold War product on ED50, with the same grid reference actually moving the target some hundreds of meters, sufficiently to be ineffective. Just for comparison, the same grid reference plotted on the local Yugoslavian TK maps would change the position by about a kilometre. Standard datums are vitally important.
3. The wide adoption of GPS has gone a long way to resolve the difficulties of standardisation of horizontal position, with WGS being universally adopted throughout NATO as the geographic coordinate system for standard digital geographic information (DGI). However, the challenges of standardisation of the vertical datum can be better appreciated if it is remembered that the maritime navigation requires the shore-line to be shown at the low water mark, land navigation shows the shore-line at mean sea level and air navigation is primarily concerned about relative height above ground level (or other hard objects). Not only does this leave a gap in information (in the inter-tidal regions), but when you add into this equation the move from traditional height references of z = zero (based on a defined tide gauge reading of sea level) - to GPS that measured "z" in absolute terms from the centre of the earth (before adjusting it back to give the user one of the various local definitions of z = zero), there is significant room for error.
4. [ARC Standard Reference.] The definition of the standard reference system can be approached from either end of the spectrum. At one end, where the system requirements are geographically limited, such as a Land Information System, the "flat world" approach can be adopted, with all the underlying geospatial information geo-coded in a local grid system, such as the British Ordnance Survey OSGB. This may be suitable for a "closed system", as long as the local grid and datum have taken into account not only the geodetic parameters required, to relate information back to the real world, but the practical requirements, of providing a unique reference system, for the GIS. At the other end, where the system is required to provide global support, or to interact with navigation and positioning functions, a "round world" solution is essential. In practical terms, the absolute accuracy of a grid system decays systematically as you move away from its defining origin and datum, with the acceptable limit of the accuracy being defined by a grid zone boundary. For practical reasons, many military map series can show the grid of two (or more systems), for example, in the area of a grid zone boundary. As a result, a single point on the ground can be represented more than once in a geographic database composed of grid raster images, each with a different grid reference associated with the relevant pixels. There are also additional technical problems over "warping" a grid raster for small scale display purposes, that further add to the difficulties and potential for errors. To meet the requirements of interoperability, at both the joint and combined force level, makes the adoption of a single, unique reference, essential for military CCIS. As a result, all Military Survey’s standard product range have been specified in ARC-WGS, to ensure the provision of a unique reference for every pixel stored in a supported geographic database. The ARC format, although requiring some transformation from source, does not excessively warp data in most parts of the globe. This is a significant benefit, when compared with some other projections that do warp data, hence significantly degrading the quality of the displayed image.
5. [International Military Standardisation.] Much of the military geographic information, used by combined and international forces, is produced and provided by participating nations. To ensure interoperability of this information, there are three international bodies involved with the military standardisation of Digital Geospatial Information used by UK Defence Forces:

a. [Digital Geographic Information Working Group (DGIWG).] DGIWG is a multinational organisation, with representatives of the geographic production agencies from eleven nations. It is principally the work of this body that has developed the military standards for the exchange of geospatial information, through the Digital Geographic Information Exchange Standard (DIGEST). Unfortunately, the requirements of international maritime navigation, articulated through the International Hydrographic Organisation (IHO), have led to concurrent development, by the hydrographic agencies, of the IHO S-57 (formerly DX-90) for hydrographic charts. Work continues to bring the two specifications into harmony, to enable the development of translators between the two different standards.

b. [NATO Geographic Conference (NGC).] The Geographic Requirements Working Group (GeoRWG) has been established by the NGC to co-ordinate the requirements of NATO nations and commands, to enable the technical developments of the DGIWG organisation to be utilised to meet the Alliance’s requirements. In the case of geospatial information, much of the technical work of DGIWG can be endorsed by NGC, or taken forward by member nations for implementation as NATO standards.

c. [NATO Military Agency for Standardisation (MAS).] MAS is responsible for the development of the NATO standards (STANAGs). In the case of geospatial information, much of the technical work is provided by DGIWG, with the subsequent STANAG work being taken forward to MAS by a DGIWG nation. This inevitably means that STANAGs lag behind DGIWG work, with some DGIWG work being adopted as national standards, in advance of STANAG promulgation.

6. [DIGEST.] DIGEST is referred to in NATO by STANAG 7074 as AGeoP-3 and has been used by NATO as the DGI "exchange" standard. It should be remembered that the DIGEST exchange standard is not necessarily suitable for use within the military CIS, but digital products built to it, can be readily imported and exploited by them. It is anticipated that the recent implementation of DIGEST 2.0 by DGIWG, will be followed this autumn by the revision of STANAG 7074, to implement the changes within NATO. Information on how to obtain a copy of DIGEST 2.0 can be obtained at "www.digest.org" where the standard can also be browsed on-line. The major changes have been the addition of a new encapsulation for raster/imagery, alignment of the DIGEST VRF with US Military Standard VPF, and revision of the geodesy sections. The significant changes include:

a. Addition of a new encapsulation for raster data that supports the NATO Secondary Imagery Format. This provides improved support for raster data sets in a manner compatible with the major developments in satellite imagery data.

b. Alignment of DIGEST with the US Military Standard VPF. The DoD VPF Standard is now a complete and compatible subset of DIGEST VRF. However, there is a growing demand for the use of the small, but significant, additional DIGEST VRF functionality which has not yet been implemented in VPF.

c. Additional capabilities added to support multiple-value attribute.

d. Alignment with latest revisions of ISO character coding standards.

e. Extension of the FACC catalogue to incorporate new areas of application, such as transportation and range value attributes in VRF relational tables.

f. Extension of the FACC catalogue to incorporate the initial results of the ongoing harmonisation between DIGEST and International Hydrographic Organisation catalogues.

g. Upgrading of the geodesy sections of DIGEST for consistency and compatibility with other sources.

h. Incorporation of corrections and clarifications accumulated since version 1.2a.

i. Editorial restructuring of the document format for ease of maintenance and text processor platform independence, including publication compatible with HTML.

j. Support of mixed data types (Raster, Matrix and Vector) within one dataset.

7. [Symbology.] You should be aware that the Military Standard vector map (VMap) product does not contain any display or cartographic symbology. As a result, vendors and developers must implement their own solution - which the end user will expect to be a reasonable facsimile of the cartographic representation on the paper map or chart. The challenges include such items as:

a. How a developer or vendor can bring into play a "rule" based system for selecting alternative representation, depending on display or output scales

b. Challenges of merging vector symbology with simultaneous displays of raster maps, without causing confusion.

c. End-user requirements to customise display for preferences such as colour and resolution.

d. Technical alternatives for cartographic feature representation, such as quick look-up tables for "dumb" graphic for point features, against slower scaleable vector representation.

8. [Symbology Standards.] Early in the development of DGI it was decided that display symbology was primarily a software development issue, and could not be incorporated into the required vendor "neutral" standard product range. However, as it has a bearing on the accuracy and acceptance of DGI, the various "standards" bodies have kept the subject under review. They are approaching the issue differently and the prevailing wisdom is that there will not be a single "plug-and-play" solution in the near future. DGIWG is amongst those following developments, such as the US DoD GeoSYM, to assess the scope for standardisation within areas such as NATO.

DEVELOPMENTS IN UK MILITARY SURVEY DGI

9. [Digital Geographic Product Information Booklet.] The Booklet is available to delegates separately. It gives information on the current range of Military Survey of products, with details of supported product specifications and standards. However, it must be remembered that many of the product specifications and standards used by UK Mil Svy are internationally controlled and outside the direct control of the agency, hence occasional changes to the specifications and standards are inevitable. Vendors and developers should appreciate that it makes both economic and system sense to have a map or chart display that can utilise this standard information and access it in the relevant product format, rather than having to go through an external translation process, which can, in Europe, lead to additional royalty charges, or even having to digitise maps on the system. The current product range is summarised in Table 1:

Table 1

Military Survey Product Range

10. [Image Map Concepts.] Many standard map series are incomplete or many years out of date, leading to difficulties in provision of operational support. Limited Defence resources, together with short deployment time-frames, make the production or maintenance of new or revised maps a considerable challenge. As a result, there can be significant shortfalls in the availability of the Standard Raster Map, such as ASRP or CRP, on which the CCIS is designed to operate. To bridge this gap, Mil Svy are developing the Raster Image Map. The specification is designed to enable the product, and the currency of its geographic information, to be geared more directly to the users requirements. This in turn will result in an optimisation of the production processes, by ensuring that, within the bounds of the specification, the product can be enhanced and reissued as time and resources permit. Ultimately, the Image Map can be used as a primary source for the production of the underlying conventional map and thus replaced. The initial problems came from the existing raster map formats not adequately handle image based products. However, some of the essential underlying principles had to be taken forward into a product that, at the machine level, should be indistinguishable from other raster maps. Key components included ARC projection, WGS co-ordinates, to give a global, seamless display for military CCIS. However, the "photo-map" feature enhancements require the inclusion of Vector information within the product, as separate VMap information is scarce and will remain so for sometime, and many current or imminent CCIS systems are not capable of fusing vector with raster.
11. [Image Map Specification.] The main components of the specification include:

a. The enhancement information, such as names, features and grid, are "fused" with the image during production, to ensure that the end product has the "look and feel" of a digital raster product.

b. The pixels are geo-coded in ARC-WGS, to correlate with the other standard raster map information providing a seamless display of all information.

c. With the imminent availability of multiple satellite platforms, to provide a wide variety of CSI, together with military imagery, the product is being designed to make the best of all of these as a "patchwork" solution during the production process. The product is designed to cater for both monochrome and colour imagery.

d. The format is most likely to be similar to CRP, that is an implementation of TIFF/GeoTIFF, in order to provide the most cost effective solution to existing, developing and future systems. A major consideration in making the final decision will be whether or not UK LAND Systems will be able to directly import the product, through adequate vendor support for GeoTIFF. The distribution medium will be CD-ROM, as part of any area coverage of raster products.

e. The density of features, in the overlay information, has to be a balance between time in production and user interpretation. However, it is anticipated that some overlay information will be required, even for "emergency response" production. Imagery enhancement, through symbolisation, is complex and requires a standard map symbol table, to enable the picture to be presented to the user in an easily recognised format. The issues that will be addressed during development include:

1. transparency of overlay info (masking of underlying features)
2. size
3. colour in normal/special conditions. note that different imagery characteristics may demand adjusted symbology. Climatic conditions in particular.

f. The product will be compressed. However the high volume and "lossless" techniques, such as the RLE compression, used for other raster map products, is perceived to be inadequate. Use of "lossy" techniques, to provide more efficient data compression [eg JPEG] is under investigation.

g. The inclusion of metadata is a key component of the utility of the product, and is essential to the information management aspect of a maintaining an effective geographic database.

12. [Image Map Standard.] As the specification develops, it is the intention to invite users, developers and vendors to comment on the product. On completion of the development, it is intended to incorporate both the hard and soft copy solutions into a single specification that will be offered to NATO for standardisation, as a substitute product.

TACISYS

13. The delivery from ULTRA Electronics, of the TACISYS fleet was completed in the summer of 1997 after a short 18 month period of prototyping and procurement, although work on developing the Esri/ERDAS software had started after the open competition in 1992. The equipment was demonstrated at last year’s conference, together with a detailed description. Since then, there has been a Post Implementation Review, which high-lighted a number of current deficiencies, either from changing user requirements or from lower levels of equipment reliability than those essential for such a critical equipment. These will be addressed in an equipment upgrade programme, planned for 1999, which will include the migration to NT. The specification has now been finalised and includes considerable built-in redundancy for critical components. The hardware migration, necessary for NT implementation, will include twin Pentium processors, with 256Mb RAM (upgradable). It is planned that the focus of software applications will be ArcView (with relevant extensions) together with ERDAS (with the VGIS module to provide Terrain Visualisation). ArcInfo will be retained for a limited range of tasks not supported within the ArcView product range. Development of the capability is continuing to include co-ordination with our allies, including the Engineer Geographic services of both the US and Canadian armies.