AERIAL PHOTOGRAPHIC COVERAGE OF IRELAND 
WITH GPS IN 12 DAYS 
Pinto L. Dip. LI.A.R. Politecnico di Milano, P.za L. da Vinci n. 32, 20133 Milano Italy. 
E-mail livio@ipmtf2.topo.polimi.it 
Cory M. Ordnance Survey of Ireland, Phoenix Park Dublin 8 Ireland. E-mail mcory@osi.ie 
Banchini G. Compagnia Generale Ripreseaeree, Via Cremonese 35/a, 43010 Fontana (PR) Italy 
Commission I, Working Group 2 
KEY WORDS: Large, Navigation, Surveing, Aerial, Photography, GPS, Performance 
ABSTRACT: 
In 1995 the Ordnance Survey of Ireland commissioned Aerial Photography of Ireland to support its small scale mapping 
programme, and the production of Orthophotos for validating farmers claims under the European Economic Commission's (EEC) 
IACS program. The photography specified was black and white, full stereo near vertical Aerial Photography at a scale of 
approximately 1:40,000. Coordination of the photo centers by GPS was required with a RMSE of 1 m. Following a tendering 
exercise, Compagnia Generale Ripreseaeree (CGR) was awarded the job based on the merit of their technical proposal, 
commitment to completing the task with GPS and their aircraft capability. As a result of unprecedented good weather during the 
summer of 1995 the aerial photography was successfully completed in 12 days. Approximately 4000 photos were taken in 77 
strips running east and west across Ireland. Because of the availability of the Learjet and the favorable meteorological conditions 
the photogrammetric crew made it possible to fly for seven hours per day while remaining within the specification of the contract. 
The automatic functioning of the camera by GPS has taken up about 9046 of the entire work. During the flight the pilot used the 
GPS system as an assisted navigational instrument. Finally, thanks to carrier phase and C/A code GPS data was recorded during 
the flight by on board GPS receivers and at 3 GPS base stations on the ground, located at previously surveyed sites, it was 
possible to calculate the path of each strip. Data post processing was effected with commercial software supplied by Leica 
operating in kinematic mode without static initialization. The distance between the airborne GPS and the nearest ground station, 
varies from a few km to a maximum of 200 km. 
1. INTRODUCTION aerial photography (in the form of digital orthophotography) 
for the purposes of validating claims made by farmers for 
The Ordnance Survey of Ireland is the state mapping agency subsidies under the Common Agriculture Policy (CAP). These 
responsible for collecting, processing and distributing Claims were supported by OS large scale (1:2500 scale) maps, 
geographical and topographical mapping information of With the areas claimed outlined by the farmer. EC Council 
Ireland required by the public and private sectors. regulation 3508/92 required an Integrated Administrative and 
One of its objectives is to provide a national up to date Control System (IACS) to be established by January 1996, 
topographic database for users of mapping and geographic which would validate the claims made by farmers. This 
information systems in support of National Economic and combined need was to be met by a contract for 1:40,000 
Social Development. In order to meet this objective, Ordnance scale, near vertical, stereo aerial photography, to be let and 
Survey are implementing a National Mapping Programme to managed by Ordnance Survey. 
meet customer driven requirements and future national ^ Many reports were being written on the benefits of controlling 
mapping needs, which includes the development of a small aerial photography using GPS, particularly in reducing the 
scales digital database, surveyed to an accuracy consistent amount of Ground Control required. Therefore this was an 
with 1:10,000 scale mapping to support graphical mapping ~~ Opportunity to examine the potential for GPS and 
products of scales in the range 1:10,000 to 1:500,000. Data photogrammetry and to test the claimed benefits. 
collection for this database is over half way complete, and the Following a tendering process, Compagnia Generale 
priority mapping product is the 1:50,000 scale 'Discovery' Ripreseaeree (CGR) from Parma (Italy) were contracted to 
map series, a widely acclaimed and technically advanced undertake the task. CGR were chosen on their technical merit, 
product which serves the tourist and general map user as well. ~~ commitment to completing the task using GPS and their 
A range of analytical and semi analytical plotters are used for Learjet capability which would provide the highest likelihood 
the small scales planimetric data collection, and up to 15 of taking advantage of the expected weather windows. Over 
Leica/Helava Digital Photogrammetric Workstations (DPW's) 20 years experience in flying aerial photography in Ireland led 
are used to collect Digital Terrain Models (DTM's) using OS to conclude it was unlikely that the contract would be 
Helava autocorrelation techniques. To date this mapping has ~~ completed in one season (April to September 1995). A 
been based on 1:30,000 scale stereo aerial photography from Previous contract, let in the 1970's took 6 years to complete 
the 1970's, but the need for up to date photography to full cover at 1:30,000 scale, therefore there was an optimistic 
complete the programme, and to maintain the mapping already ~~ expectation of only 60% coverage in the first year for this 
undertaken became urgent. project. 
In addition to this mapping requirement the Department of 
Agriculture, Food and Forestry (DoAFF) required up to date 
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International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B1. Vienna 1996 
  
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