Positional Control in the 1:25000 Cartography, Oporto Region

Size: px

Start display at page:

Download "Positional Control in the 1:25000 Cartography, Oporto Region"

Eric Porter
6 years ago
Views:

1 Rui DIAS ad Rui TEODORO, Portugal Key words: Accuracy, data acquisitio, quality cotrol, cartography SUMMARY The Portuguese Army Geographic Istitute (IGeoE), beig aware of the importace of the positioal accuracy of the geographic iformatio, as a atioal referece etity, evaluates periodically the accuracy of the geographic iformatio it produces. Now it s i productio the Oporto Block cosistig of 1:5 000 scale sheets, bouded o the orth by Povoa de Varzim, o the south by Espiho, o the east by Castelo de Paiva ad o the west by the Atlatic Ocea, beig already cocluded the restitutio operatios ad beig the iformatio used at the momet by the Survey Sectio to complete ad fiish the data acquisitio process. The IGeoE ivested huma ad material resources o the developmet of methodologies havig i mid the moitorig of the positioal accuracy of the Official Cartography that it produces throughout the differet phases of the data acquisitio process, described i this article. 1/1

2 Rui DIAS ad Rui TEODORO, Portugal 1. INTRODUCTION Accordig to the Iteratioal Stadards, ISO19113 ad ISO19114, the positioal accuracy is oe of the elemets of the geographic iformatio quality, havig a essetial role sice the begiig of the process of the cartography productio, beig impossible for a producer of geographic iformatio to eglect this elemet, beig ecessary to esure the quality stadards required for each scale. This will coditio the whole productio process, requirig the implemetatio of processes ad methodologies which guaratee the positioal accuracy required to cartography. For the productio of the Military Maps of the Oporto Block (Figure 1), the digital aerial photographs at 1: scale, have bee trasferred to IGeoE beig the photogrammetric support, the aerotriagulatio ad the restitutio a resposibility of IGeoE. Thus, this article aims to describe the procedures used by IGeoE i the process of data acquisitio for the Military Maps, as well as the oes to moitorize the positioal accuracy of those data, i what refers to the Oporto Block. Figure 1 - Framework of Oporto Block, for the 1:5 000, M888 Series.. DATA ACQUISITION PROCESS.1 Survey of photogrammetric poits The survey of Photogrammetric Poits (PP) cosists i collectig three-dimesioal coordiates, i the field, of well defied poits o the earth surface ad clearly visible i aerial photography (Figure ), havig i mid the aerotriagulatio. This task is performed by the IGeoE Survey Sectio. The PP are selected o the aerial photographs, accordig to the framework of the photogrammetric flight, with a average desity of 1 PP per 1:5 000 sheet (each sheet covers a area of 160 km resultig from a 16km legth by 10 km width). The Survey Sectio performs the field acquisitio of those coordiates with the support of the SERVIR (Sistema de Estações de Referêcia VIRtuais) CORS (Cotiuous Operatig Referece Statios) etwork. This etwork was implemeted ad is maaged by that Sectio. Cosistig owadays of 7 GNSS (Global Navigatio Satellite System) base statios distributed throughout the mailad territory, it uses the VRS (Virtual Referece Statio) /

The distributio of the statios is the followig: Figure Distributio of CORS etwork.

3 techique to calculate the differetial correctios that are seded to the users o the field, usig GPRS (Geeral Packet Radio Service) protocol preferetially. The distributio of the statios is the followig: Figure Distributio of CORS etwork. To the Oporto Block 9 photogrammetric poits have bee coordiated, havig each oe of them a positioal accuracy better tha 0.05 m (Afoso et al, 007). Groud photo Map Aerial photo Figure 3 - Example of a photogrammetric poit of Oporto block. 3/3

. Aerotriagulatio The Aerotriagulatio (AT) is the process of assigig groud cotrol values to poits o a block of photographs by determiig the relatioship betwee the photographs ad kow groud cotrol poits.

4 . Aerotriagulatio The Aerotriagulatio (AT) is the process of assigig groud cotrol values to poits o a block of photographs by determiig the relatioship betwee the photographs ad kow groud cotrol poits. This block is composed of several partial models, mathematically similar to the object, usig the support available o the field. I the AT of the Oporto Block a covetioal aerotriagulatio was doe, havig bee used oly photogrammetric poits i the calculatio ad adjustmet of the AT. The exteral orietatio parameters of aerial photographs (X0, Y0, Z0, ω, φ ad κ) were despised, ie the coordiates of the projectio ceter ad the rotatio of optical axis at the time of the shootig were t used, because there is o iformatio about their precisio. The result of the AT (Figure 4) is aalyzed after the fial calculatios are fiished. The AT results are oly accepted if they are withi the parameters defied previously. Figure 4 - Aerotriagulatio results..3 Positioal Accuracy of the Aerotriagulatio After completig the AT, it is verified its positioal accuracy, for which were used 33 idepedet poits (geodetic bechmarks both horizotal ad vertical), distributed alog the Oporto Block. Two readigs were made (model coordiates) to each cotrol poit at the photogrammetric workstatio, havig bee cosidered the average value of those readigs for the fial coordiates of each cotrol poit. As true value were used the coordiates of the geodetic bechmarks, measured durig the photogrametric poits survey. I order to estimate the accuracy i the calculatio ad adjustmet of the aerotriagulati it was used the Root Mea Square Error (RMSE) ad obtaied a value of 0.44 m for plaimetry (1) ad 0.51 m for the height (). 4/4

5 RMSE MP = ( E E ) + ( N N ) i= 1 i= 1 1 (1) Where: E, N - True value of plaimetric coordiates of the poit i. E, N - plaimetric coordiates read i the photogrammetric workstatio of the poit i. is the umber of cotrol poits. RMSE Z = i= 1 ( Z Z ) 1 () Where: Z - True height, of the poit i Z - height read i the photogrammetric workstatio, of the poit i. is the umber of cotrol poits..4 Restitutio Restitutio is the process of iterpretig the existig iformatio i the stereoscopic model (by the photogrammetrist), followed by the respective acquisitio, accordig to the IGeoE Data Catalogue. The restitutio of iformatio for the Military Maps is performed accordig to the Rules of Acquisitio, to esure homogeeity of the iformatio i all the atioal territory. Besides the cotet errors (omissios ad / or cofusios) that might appear at this acquisitio phase, i what respects to the positioal accuracy of the iformatio acquired, positioal errors ca be added related with the photogrammetrist stereoscopic skills. So, to esure that all photogrammetrists have the ecessary requiremets for the acquisitio of data for the Military Maps, stereoscopic acuity tests are doe, o a regular basis, havig all the iterveiets the classificatio of GOOD, with a error i the height less tha 0.5 m. 3. POSITIONAL CONTROL OF THE GEOGRAPHIC INFORMATION 3.1 Cotrol poits The choice of cotrol poits was doe radomly havig i mid a homogeeous distributio throughout the study area. They are oly plaed where it is possible to establish a uequivocally correspodece betwee the acquired poit o the photogrametric workstatio ad the poit measured o the field. So, the uiverse was substatially reduced, havig the cotrol bee limited to objects i which real geometry ad the geometry of represetatio i the Military Maps is the same, with well defied agles. Examples of this are buildigs, walls ad feces. A total of 104 cotrol poits were plaed ad measured usig GNSS equipmets, with support of the SERVIR CORS etwork These were the True coordiates. To the same 5/5

6 poits it was cosidered the coordiates measured i the workstatio i the vector data file. 3. Results After a first aalysis, the poits measured o the field that did t match the poits acquired by the photogrammetrist were removed of the sample, havig resulted 101 cotrol poits to calculate the positioal accuracy of the vector data. For those poits was calculated the RMSE for plaimetry (3) ad altimetry (4). RMSE MP = ( E E ) + ( N N ) ic i= 1 i= 1 1 Where: E, N - True plaimetric coordiates to the poit i. E ic, N ic - plaimetric coordiates to the poit i, extracted from the vector data. is the umber of cotrol poits. ic (3) i= 1 RMSE = Z ( Z Z ) 1 ic (4) Where: Z - true height, for the poit i. Z ic - height to the poit i, extracted from the vector data. is the umber of cotrol poits. It was obtaied a RMSE of 1,0 m for the plaimetry ad a RMSE of 1,04 m for the height. Was also aalyzed the distributio of errors alog the Oporto Block. The result was a homogeeous distributio (Figure 4), ot havig bee registered ay ifluece either from the type of relief or due to the photogrametrist. 6/6

7 Less tha 0.5 m 0.5 m 1.0 m 1.0 m 1.5 m 1.5 m.0 m More tha.0 m Plaimetry Height 4. Coclusio Figure 5 - Distributio of errors. The geographic iformatio of the Military Maps 1:5 000, Série M888, achieves ad exceeds all the elemets of positioal accuracy required ot oly to the cartography of medium scales, but also to the cartography of higher scale. This study also allowed to validate the methods ad processes used by IGeoE i the productio of its cartography. IGeoE keeps assertig as a producer of cartography of high quality ad accuracy. REFERENCES Afoso, A., Lopes, J.,Dias, R., (009), Cotrolo de Qualidade Posicioal da Cartografia Militar do IGeoE em ETRS89. I: LIDEL (eds.). Cartografia e Geodesia 009, Caldas da Raíha, Portugal, pp Afoso, A., Martis, F., J.,Dias, R., Medes, V. (007), O projecto SERVIR do IGeoE e suas aplicações. I: LIDEL (eds.). Cartografia e Geodesia 007, Lisboa, Portugal, pp Afoso, A., Dias, R., Teodoro, R., (006), IGeoE: Positioal quality cotrol i the 1/5000 cartography. Joural. 7th Iteratioal Symposium o Spatial Accuracy Assessmet i Natural Resources ad Evirometal Scieces, 5 ato 7 de July 006, Lisbo. Mira, J. (008), Cotrolo de Qualidade da Cartografia do Bloco de Lisboa produzida o Istituto Geográfico do Exército. Boletim do IGeoE, Nº Rossa, J. (00), A exactidão posicioal em cartografia digital. Boletim do IGeoE, Nº /7

8 BIOGRAPHICAL NOTES Rui Dias is the Head of the Photogrammetry Sectio of the IGeoE sice July 009. Before he was the Head of the Survey Sectio. He holds a Geographic Egieer degree by the Faculty of Scieces of the Uiversity of Lisbo. He published several papers related with CORS etworks ad quality cotrol of the geographic iformatio. Rui Teodoro is the Head of the Survey Sectio of the IGeoE sice July 009. Before he was the Chief of the Survey Teams. He holds a Geographic Egieer degree by the Faculty of Scieces of the Uiversity of Lisbo. He is also a professor at the Military Academy ad at the Iteral Security ad Police Scieces Istitute. He published several papers related with CORS etworks, vector data geeralizatio ad survey practical applicatios. CONTACTS Rui Dias Portuguese Army Geographic Istitute Aveida Dr. Alfredo Besaude Lisboa Portugal Tel Fax ruidias@igeoe.pt Web site: Rui Teodoro Portuguese Army Geographic Istitute Aveida Dr. Alfredo Besaude Lisboa Portugal Tel Fax rteodoro@igeoe.pt Web site: 8/8

CENTRIFUGAL PUMP SPECIFIC SPEED PRIMER AND THE AFFINITY LAWS Jacques Chaurette p. eng., Fluide Design Inc. November 2004

CENTRIFUGAL PUMP SPECIFIC SPEE PRIMER AN THE AFFINITY LAWS Jacques Chaurette p. eg., Fluide esig Ic. November 004 www.fluidedesig.com There is a umber called the specific speed of a pump whose value tells