GPS方法在宗地測繪的應(yīng)用PAGEPAGE22（此文檔為word格式，下載后您可任意編輯修改?。〨PS方法在宗地測繪的應(yīng)用

Paperpreparedfor:ACSM/ASPRSCONVENTIONCharlotte,NorthCarolinaFebruary27-March2,1995摘要本文闡述了一種包括地籍測繪和成圖的GPS方法。它考慮到阿爾巴尼亞的現(xiàn)實和具體需求，同時也和其他相關(guān)的發(fā)展中國家地籍和土地登記制度（CLRS）形成相關(guān)聯(lián)。該方法被闡述了規(guī)劃和準(zhǔn)備，現(xiàn)場程序，數(shù)據(jù)處理。后半部總結(jié)了該領(lǐng)域在阿爾巴尼亞進(jìn)行的實地測試，以檢驗和完善此方法。該方法利用一個新的“亞米”接收器“（開拓者XL）在差分模式下提供精確到一米左右的精度。1背景阿爾巴尼亞是巴爾干小國，位于希臘（南），前南斯拉夫共和國（北部和東部），和亞得里亞海（西部）之間。它擁有約28,000平方公里的面積，這和比利時的大小相當(dāng)，或相當(dāng)于美國馬里蘭州。在國內(nèi)生產(chǎn)總值（GDP）和其他福利指標(biāo)方面，阿爾巴尼亞是歐洲最窮的國家。該國人均年收入約3.3萬美元（世界銀行1992)同該地區(qū)的許多國家一樣，阿爾巴尼亞最近就從計劃經(jīng)濟(jì)轉(zhuǎn)變?yōu)橐允袌鰹樵瓌t的經(jīng)濟(jì)體制。這種轉(zhuǎn)變的一個基本組成部分就是土地使用權(quán)的私有化和便利的土地市場。在共產(chǎn)主義時期的農(nóng)業(yè)用地大部分屬于國營農(nóng)場和合作社組織，阿爾巴尼亞這片土地自1991年以來，已被重新分配到各個家庭。據(jù)估計分配方案將涉及約250萬塊宗地和房屋拆遷（Jazoj等1994）。大多數(shù)農(nóng)村土地被分配到各個家庭。阿爾巴尼亞面對的挑戰(zhàn)是在開始銷售，繼承和其他形式的土地貿(mào)易之前完成地籍簿和土地登記地籍系統(tǒng)(CLRS)的轉(zhuǎn)換。由于需要測繪個別地塊以確定宗地所登記的包含權(quán)利人以及他們的權(quán)利的性質(zhì)的空間尺寸的法律文件，分的地塊大?。ㄆ骄s0.3公頃），以及持有土地的零散，使得在緊迫的時間限制的情況下設(shè)計和實施都顯得非常困難，本文介紹了一種對工程進(jìn)行設(shè)計的方法,將提供一個快速和負(fù)擔(dān)得起的手段測繪宗地、單體建筑(在城市地區(qū))。并將使測繪土地和個別大廈（市區(qū)）快速和負(fù)責(zé)任地進(jìn)行。2測量和繪圖在阿爾巴尼亞在阿爾巴尼亞的測量和繪圖主要是三個政府機(jī)構(gòu)的責(zé)任。土地研究所（卷曲度）負(fù)責(zé)在農(nóng)村地區(qū)的調(diào)查和測繪。地圖通常是1:5000的比例尺，然而他們不產(chǎn)生其他尺度的地圖（如1:2500）。大部分城市測繪涉及地質(zhì)和大地測量企業(yè)（專家組）。城市測繪最重要的比例尺尺度是1:500和1:200。軍事地形學(xué)研究所（MTI公司）負(fù)責(zé)全國地圖系列（1:50000）。和許多其他欠發(fā)達(dá)的國家中不同，在很多情況下阿爾巴尼亞擁有稠密的的大地測量控制點網(wǎng)絡(luò)（約4公里的密度），該網(wǎng)絡(luò)明確劃定了高三腳架信號的密集網(wǎng)絡(luò)。臨時使用的gps（微星1992）試驗證實，該網(wǎng)絡(luò)具有很高的精確度。阿爾巴尼亞是幸運的，擁有許多畢業(yè)于達(dá)拉納市理工大學(xué)的受過5年良好教育的測量師（估計約300）。課程包括前三年扎實的數(shù)學(xué)和測量科學(xué)基礎(chǔ)。后兩年是比大多數(shù)測量項目更一般的與生態(tài)學(xué)，城市規(guī)劃，采礦技術(shù)，送水工建設(shè)等不同主題相關(guān)的調(diào)查方案。與過去的20年相似，每年約20％的測繪項目畢業(yè)生學(xué)生仍在從事測量工作。大部分的這些畢業(yè)生目前失業(yè)或參與一些其他工作。也有一個調(diào)查顯示，那些測繪專業(yè)技術(shù)人員都在中等學(xué)校（相當(dāng)于美國中）。這些擁有資格的人的數(shù)量估計在500人。他們在測繪領(lǐng)域的專業(yè)知識，似乎足以支持CLRS的發(fā)展。然而，鑒于土地法的急劇變化和引進(jìn)的地籍法律，額外的培訓(xùn)和教育，中等學(xué)校培訓(xùn)的測繪師的技能和專業(yè)知識需要更新。目前在阿爾巴尼亞存在的整套地圖，尤其是在大比例尺（1:500-1:10,000）地圖，為在一個土地管理信息系統(tǒng)上建立一個有效的地籍系統(tǒng)提供了寶貴的基礎(chǔ)。除了這個地圖信息，LRI有很好的組織和參考檔案的調(diào)查記錄,一套控制致密化處理(三角)方法和,其他的視距導(dǎo)線調(diào)查方法。也許是最具挑戰(zhàn)性的是阿爾巴尼亞局的現(xiàn)實情況，破碎的非常微小的土地碎片。在許多情況下,村民被分配到一至四塊的土地(法律允許多達(dá)七塊宗地)。這些個別的宗地可能相距幾公里，涉及農(nóng)用地以及含有橄欖樹（定義在樹木的數(shù)量方面）的牧場土地。從測繪的角度來看，CLRS必須在這種呈現(xiàn)出復(fù)雜分化的環(huán)境中，找出符合成本效益的解決方案。3全球定位系統(tǒng)方法的說明在阿爾巴尼亞測試和實施利用GPS的方法被稱為“差分偽距定位”技術(shù)。這種技術(shù)需要至少兩臺GPS接收機(jī)。

'參照'或'基地'接收機(jī)占據(jù)一個已知的大地測量控制點，'遠(yuǎn)程'或'流動站的接收機(jī)是用來測量宗地碎部。參考接收器收集到的數(shù)據(jù)被用來計算更正（ΔX，ΔY，ΔZ）偽距測量。這些差分改正直接被應(yīng)用到遙控接收器的后處理過程中。這些修正的幅度是常見的兩個單位，提供參考的接收機(jī)和遙控裝置之間的距離并不太大。該技術(shù)能夠在宗地角落達(dá)到亞米精度。作為流動站接收機(jī)和參考接收機(jī)的單頻Trimble4000SE儀器使用Trimble探路專業(yè)XL方法進(jìn)行測試。該技術(shù)具有以下優(yōu)點：實現(xiàn)相對簡單強(qiáng)大的觀測技術(shù)，因此需要最少的培訓(xùn),只需要一個基站支持便可多個流動站（可以在一個相對較低的成本下顯著增加生產(chǎn)力）流動站單位之間不需要協(xié)調(diào)（因此現(xiàn)場工作人員可以彼此獨立運作（4）占用時間很短（30秒）該方法的概括性描述方面是下面劃線四類:計劃和準(zhǔn)備、現(xiàn)場程序、后期處理,大地的考慮。4分部計劃和準(zhǔn)備4.1衛(wèi)星覆蓋全面規(guī)劃和組織的GPS方法是必不可少的一部分。因此，調(diào)查之前，必須評估在特定時間上感興趣的區(qū)域的衛(wèi)星覆蓋。最近星歷數(shù)據(jù)也是必需的，它描述了最新衛(wèi)星星座軌道參數(shù)。通過利用GPS接收機(jī)，對至少一顆衛(wèi)星進(jìn)行大約15分鐘的星歷數(shù)據(jù)收集。這將確保獲得完整的導(dǎo)航信息。收集到的數(shù)據(jù)被下載到個人計算機(jī)（PC）。被任務(wù)規(guī)劃軟件（例如快速的TRIMBLE計劃）用于生成的衛(wèi)星能見度圖表和數(shù)量的報告。該圖描繪“的PDOP能快速評估是否有足夠的衛(wèi)星覆蓋，同時為確定”衛(wèi)星的數(shù)量“提供一個方便的手段，即至少4顆衛(wèi)星，PDOP值低。PDOP值是一個衛(wèi)星星座的幾何強(qiáng)度的指標(biāo)。4.2建立一個數(shù)據(jù)字典數(shù)據(jù)字典的定義是有關(guān)數(shù)據(jù)的結(jié)構(gòu)和使用信息的目錄。它是用來組織和指導(dǎo)數(shù)據(jù)收集過程。每個字典包含列表的功能，每個功能的屬性列表，以及每個屬性的值列表。例如宗地比例尺，被視為測量的一個單一方面。如“'日期'和'時間'的屬性也包括在內(nèi)。在市區(qū)的測量需要更詳細(xì)的字典（包括功能，如“電線桿”，“建設(shè)園地”，“道路'，'混凝土掩體”，“籬笆角落”等）。一旦數(shù)據(jù)字典被創(chuàng)建，它將被上傳到數(shù)據(jù)采集器上一方便在該領(lǐng)域的后續(xù)使用。4.3相應(yīng)的接收器配置開拓者XLGPS接收器是唯一可能在特定的操作條件(如記錄時間間隔，截止高度角，PDOP，SNR（信噪比））實現(xiàn)亞米級精度的儀器。記錄間隔指定位置接收器內(nèi)存儲的規(guī)律。可以收集到的數(shù)據(jù)量受到接收器的內(nèi)部存儲器容量大小的限制。5秒的時間間隔為生成的數(shù)據(jù)之間提供了平衡，在每個點上流動站需要占用時間，海拔初始值應(yīng)設(shè)置為10，以排除衛(wèi)星過于接近地平線，因為大氣的影響可能會導(dǎo)致信號衰減。PDOP掩碼誤差值調(diào)整到8目的是確保數(shù)據(jù)收集時只有一個良好的衛(wèi)星星座的存在。信噪比確保一定強(qiáng)度的測量信號被接受到。信噪比應(yīng)避免低于4，這是因為低信號強(qiáng)度會影響定位精度。4.4流動站接收機(jī)配置應(yīng)以同樣的方式配置流動站接收機(jī)作為基準(zhǔn)站接收機(jī)，但也有以下例外。要求微分修正過程的要求是追蹤衛(wèi)星基站的一個子集。截止高度角（150）的PDOP掩碼（6），信噪比掩碼（6）的值設(shè)置比流動站接收機(jī)更嚴(yán)格。5勘測領(lǐng)域Procedurea）在效率和生產(chǎn)力得到最大限度的發(fā)揮的條件下，詳細(xì)的勘測是實地考察的重要部分。這適用于所有的測量技術(shù)，在GPS測量上更是如此?？睖y的第一步是找出適合的現(xiàn)有的大地測量控制點。同時選定的控制點應(yīng)是可使用的，最好是車輛可到達(dá)的，應(yīng)該有一個開放的視野。其次，必須實地踏勘需要測量的區(qū)域，以便在測量過程繪制地籍草圖級草圖。這些程序利用這些方法優(yōu)化測量過程，并以一個嚴(yán)密的方式進(jìn)行組織。5.1設(shè)置相應(yīng)的接收器基準(zhǔn)站接收機(jī)可以是一個持續(xù)運營的中央基站，或架設(shè)在調(diào)查區(qū)域附近的控制點上。天線高度，連同其他有關(guān)資料（如站名，日期，時間，天氣條件），必須進(jìn)行測量和記錄。要小心謹(jǐn)慎,確?；臼鞘占瘮?shù)據(jù)在羅孚接收器,因為只有同時基地和羅孚接收器之間的數(shù)據(jù)可能隨之差異修正。測量過程要細(xì)心，以確保基站和任何流動站接收機(jī)收集數(shù)據(jù)之前不會有較大誤差，因為基準(zhǔn)站和流動站接收機(jī)之間的同步數(shù)據(jù)可能在隨后產(chǎn)生差分改正。理想的基地接收機(jī)應(yīng)設(shè)立在中央基站和調(diào)查區(qū)域（或在第二個集中式基站）附近的一個控制點上。這為測量工作提供了一種有價值的檢查，也可作為因沒電而終止工作的接受機(jī)的一個備份。架設(shè)第二個基準(zhǔn)站接收機(jī)被認(rèn)為過于昂貴的，因此重要的是采用其他檢查GPS結(jié)果方法。（例如對大型地圖上顯示的一些測量功能檢查）5.2數(shù)據(jù)收集與流動站接收機(jī)流動站接收機(jī)（探路者PROXL）可以放在一個背包內(nèi)，天線安裝在一個范圍極，由操作員進(jìn)行數(shù)據(jù)采集。這樣非常適合地籍測量所需的流動性。然后可以在村領(lǐng)導(dǎo)/長輩的帶領(lǐng)下進(jìn)行每塊宗地角落的測定，進(jìn)行每個點的GPS數(shù)據(jù)采集（30秒），和一個領(lǐng)域草圖的注釋。5.3區(qū)域草圖現(xiàn)場草圖是數(shù)據(jù)收集的一個重要組成部分，構(gòu)成寶貴的邊界證據(jù)。由于具有GPS測量點的位置，在后處理階段，連接這些點，劃定邊界線，在地籍圖上顯示。因此，最重要的是在該區(qū)域做好記錄，,最好由沒有參與這項數(shù)據(jù)收集過程的一方進(jìn)行。草圖應(yīng)該盡可能清楚地描繪出地名,地標(biāo)描述,確定的一條邊界線作為分界線,宗地的編號、及其他相關(guān)領(lǐng)域的信息。在進(jìn)行的試驗(見下一章節(jié))這往往被證明是最具挑戰(zhàn)性的一部分,現(xiàn)場調(diào)查。允許最好在數(shù)據(jù)收集過程中不涉及黨的可靠的一代，地籍圖。應(yīng)盡可能清楚地描繪草圖點名稱，碑的描述，在現(xiàn)場，任何包裹的識別號碼，以及其他相關(guān)領(lǐng)域的特點決定的邊界線。實地考察

（見下一節(jié)）往往被證明是在進(jìn)行的測試中最具挑戰(zhàn)性的部分。6后處理每天工作結(jié)束后，應(yīng)將數(shù)據(jù)下載到PC，并在進(jìn)行任何處理之前存檔在一個可移動的軟盤里。這確保了所有原始數(shù)據(jù)的副本，目的是出于安全原因，維護(hù)。差校糾正過程可分為以下步驟：指定和準(zhǔn)備的基礎(chǔ)數(shù)據(jù)文件（S）輸入基站參考坐標(biāo)指定和準(zhǔn)備流動站數(shù)據(jù)文件（S）差分改正數(shù)據(jù)變換結(jié)果，以當(dāng)?shù)貫榛鶞?zhǔn)?？梢允褂肞FINDER軟件的功能執(zhí)行這些步驟。接收器收集和存儲的所有數(shù)據(jù)都與WGS84參考橢球相關(guān)。這些數(shù)據(jù)應(yīng)該在WGS84坐標(biāo)系內(nèi)進(jìn)行一次處理并轉(zhuǎn)換為當(dāng)?shù)氐幕鶞?zhǔn)，一旦處理已經(jīng)完成（詳情請參閱節(jié)大地注意事項）?；緫?yīng)將WGS84橢球的參考坐標(biāo)輸入，這可能是要獲得這些坐標(biāo)轉(zhuǎn)從本地數(shù)據(jù)到WGS84轉(zhuǎn)化的位置。轉(zhuǎn)換應(yīng)格外小心，因為任何錯誤的基礎(chǔ)參考位置將在宗地的坐標(biāo)有類似幅度的反應(yīng)。

包含有差分改正流動站位置并在數(shù)據(jù)采集器編譯的數(shù)據(jù)屬性必須轉(zhuǎn)換為符合繪圖軟件的格式。一般來說，AutoCAD或一個比較流行的GIS（如ArcInfo級別）將被用來存儲和管理地籍?dāng)?shù)據(jù)庫存儲。PFINDER可以將數(shù)據(jù)導(dǎo)出到不同的制圖和地理信息系統(tǒng)軟件包。7地圖制作地籍圖是以提供土地登記和地籍為目的明確說明，顯示在一個司法管轄區(qū)的所有宗地。地籍圖在法律上描述為所有已登記的宗地。地籍圖或地籍重疊也代表了一種多用途的LIS/GIS的屬性層，因此，必須是能夠與其他層的信息集成，如自然資源，基礎(chǔ)設(shè)施和社會經(jīng)濟(jì)的主題。

計算機(jī)輔助繪圖軟件（AutoCAD版本11），在阿爾巴尼亞進(jìn)行地籍圖的生產(chǎn)測試期間的使用。應(yīng)該指出的是，產(chǎn)生的可靠的數(shù)據(jù)表明，在數(shù)據(jù)收集過程對編制全面草圖的高度依賴。8在阿爾巴尼亞大地測量的思考GPS技術(shù)在阿爾巴尼亞的使用提出了一些重要的大地測量問題。正如之前提到的，所有的GPS數(shù)據(jù)相關(guān)的定義都涉及到了1984年世界大地測量系統(tǒng)（WGS84）。該系統(tǒng)是一個以地球中心為原點，地球固定的3維坐標(biāo)系統(tǒng)，作為整個地球的橢球它能最好的吻合地球表面。當(dāng)?shù)氐拇蟮鼗鶞?zhǔn)點是根據(jù)Krassowsky橢球。因此，阿爾巴尼亞的基準(zhǔn)是本地的最佳擬合橢球。正因為如此當(dāng)?shù)貦E球和全球地心參照系統(tǒng)之間的關(guān)系是不容易確定，使得這些坐標(biāo)系統(tǒng)之間難以實現(xiàn)精確的轉(zhuǎn)換。最后的位置可能已經(jīng)被轉(zhuǎn)化為阿爾巴尼亞本地使用的坐標(biāo)系統(tǒng)中。這種轉(zhuǎn)換方法還需要參考站的的WGS84系統(tǒng)坐標(biāo)。9結(jié)論在佛羅里達(dá)大學(xué)進(jìn)行的試驗表明，甚至當(dāng)基準(zhǔn)站和流動站之間的基線距離為135公里時米級精度也是可以實現(xiàn)的。這意味著，大多數(shù)地籍測繪，沒有必要投資于昂貴和費時的控制網(wǎng)致密化工程。與傳統(tǒng)的測量和測繪方式相比，GPS方法具有顯著優(yōu)勢，不管是在辦公室和外地生產(chǎn)相比較。此外，它不依靠現(xiàn)有的地圖，并提供數(shù)字格式，可以很容易地轉(zhuǎn)換為電腦繪圖系統(tǒng)或地理信息系統(tǒng)中的數(shù)據(jù)。由于缺乏埋石和臨時性質(zhì)的個人界址，建議在較大區(qū)域內(nèi)的小宗地測量上繼續(xù)使用繼續(xù)傳統(tǒng)的方法。最后，應(yīng)重新強(qiáng)調(diào)的關(guān)鍵是它的速度和不確定性能否滿足阿爾巴尼亞和其他許多發(fā)展中國家的測量和測繪標(biāo)準(zhǔn)?；谠诎柊湍醽啱@得顯著成果的基礎(chǔ)上，我們覺得，本文中所描述的gps方法提供了一個可行的和極具吸引力的替代目前正在使用的其他方法的方案。致謝這項工作轉(zhuǎn)包于通過從土地權(quán)屬中心土地市場開發(fā)項目。它是由美國威斯康星大學(xué)（LTC）的美國國際開發(fā)署資助的。作者感謝長期工作的人員（尤其是大衛(wèi)·斯坦菲爾德和鄧麗君巴里），美國國際開發(fā)署，以及ICC在阿爾巴尼亞的支持。參考文獻(xiàn)[1]Barnes,G.,D.Moyer,B.Chaplin,M.Sartori,R.ShresthaandE.DesRoche(1994)."TheDesignandComparativeEvaluationofaGPSMethodologyforCadastralSurveyingandMappinginAlbania."FinalReportpreparedfortheLandTenureCenter,UniversityofWisconsin,Madison,87p.[2]MSI(1992)."GeodeticOverviewforLandRegistrationandMappinginAlbania."ReportpreparedfortheLandTenureCenter,UniversityofWisconsin,MadisonbyMeasurementScienceInc.[3]Jazoj,A.,S.LamaniandL.Lira(1994)."SurveyingandMappingStrategyforSupportingEmergingLandMarket."PaperpresentedatGIS/LIS'94,Budapest,Hungary,13-17June,1994,20p.[4]Sjoberg,O.(1991).SocialStructureinAlbanianDiscourse."DraftmanuscriptpreparedforpublicationinHandbookonSouthEasternEurope(Ed.K.Grothusen).Gottingen:Vandenhoeck&Ruprecht,26p.[5]WorldBank(1992)."AnAgriculturalStrategyforAlbania."ReportpreparedbyaJointTeamfromTheWorldBankandTheEuropeanCommunity,265p.

AGPSMETHODOLOGYFORSURVEYINGANDMAPPINGCADASTRALPARCELSGrenvilleBarnes,MichaelSartoriUniversityofFlorida(Gainesville)BruceChaplinMeasurementScience,Inc(Denver)ABSTRACTThispaperdescribesaGPSmethodologyforcadastralsurveyingandmappingattheparcellevel.ItwasdesignedtotakeintoaccounttheparticulardemandsandrealitiesofAlbania,butitalsohasrelevancetootherdevelopingcountrieswhichareintheprocessofdevelopingacadastreandlandregistrationsystem(CLRS).Themethodologyisdescribedintermsofofficeplanningandpreparation,fieldprocedures,post-processing,andgeodeticconsiderations.ThelatterpartofthepapersummarizesthefieldteststhatwereundertakeninAlbaniainordertotestandrefinethemethodology.Themethodologymakesuseofanew"sub-meter"receiver(PathfinderPROXL)whichisusedinadifferentialmodetoprovideaccuraciestoaroundonemeter.1BACKGROUNDAlbaniaisasmallBalkancountrylocatedbetweenGreece(tothesouth),theex-republicofYugoslavia(tothenorthandeast),andtheAdriaticSea(tothewest).Itisapproximately28,000squarekilometersinarea,whichisequivalenttothesizeofBelgiumorthestateofMarylandintheUS.IntermsofGrossDomesticProduct(GDP)andotherwelfareindicators,AlbaniaisthepoorestcountryinEurope.Thepopulationofthecountryisaround3.3million(WorldBank1992).Likemanycountriesintheregion,Albaniahasrecentlymovedfromacentralized,commandeconomytoonebasedonmarketprinciples.Afundamentalpartofthistransformationinvolvestheprivatizationoflandrightsandthefacilitationofalandmarket.Duringthecommunisteramostoftheagriculturallandwasorganizedintostatefarmsandcooperativesandsince1991Albaniahasbeenredistributingthislandtoindividualfamilies.Itisestimatedthatthedistributionprogramwillinvolvesome2.5millionlandparcelsandhousingunits(Jazojetal1994).Themajorityofthelandinruralareashasalreadybeenallocatedtoindividualfamilies.ThechallengefacingAlbaniaistoputinplaceacadastreandlandregistrationsystem(CLRS)beforelandstartschanginghandsthroughsales,inheritancesandothertransactions.Thismeanssurveyingandmappingindividualparcelsandregisteringalegaldocumentwhichidentifiesthespatialdimensionsoftheparcel,rightholdersandthenatureoftheirrights.Theminutesizeofthelandparcels(averageofabout0.3hectares),aswellasthefragmentednatureoflandholdings,makesitextremelydifficulttodesignandimplementaCLRSwithinthetighttimeconstraints.Thispaperdescribesaprojectwhichwasundertakentodesignamethodologythatwouldprovidearapidandaffordablemeansofsurveyingandmappinglandparcelsandindividualbuildings(inurbanareas).2SURVEYINGANDMAPPINGINALBANIASurveyingandmappinginAlbaniaisprimarilytheresponsibilityofthreegovernmentagencies.TheLandResearchInstitute(LRI)isresponsibleforsurveyingandmappinginruralareas.Themappingisgenerallyatascaleof1:5000,althoughtheydoproducemapsatotherscales(e.g.1:2500).TheGeologyandGeodesyEnterprise(GGE)dealswithmostoftheurbansurveyingandmapping.Mostofthismappingisdoneatscalesof1:500and1:200.TheMilitaryTopographicInstitute(MTI)isresponsibleforthenationalmapseries(1:50000andsmaller).Unlikemanyotherlessdevelopedcountries,Albaniahasadensenetworkofgeodeticcontrolpoints(approximately4Kmdensity)whichinmanyinstancesareclearlydemarcatedbymeansoftalltripodsignals.ProvisionaltestsusingGPS(MSI1992)confirmthatthisnetworkhasbeensurveyedtoahighdegreeofaccuracy.Albaniaisfortunatetohavearelativelyhighnumber(estimatedataround300)ofwelleducatedsurveyorswhohavegraduatedfromthe5-yearsurveyingprogramatthePolytechnicUniversityofTirana.Thecurriculumincludesastrongmathematicalandmeasurementsciencefoundationinthefirstthreeyears.ThelattertwoyearsaremoregeneralthanmostsurveyingprogramsanddealwithsuchdiversetopicsasEcology,UrbanPlanning,MiningTechnology,andHydrotechnicConstruction.Thesurveyingprogramgraduatesapproximately20studentsperyearandhasapparentlymaintainedthislevelforthepast20years.Alargemajorityofthesegraduatesarecurrentlyunemployedorareinvolvedinsomeotherlineofwork.TherearealsoanumberofsurveytechnicianswhohavespecializedinsurveyingattheMiddleSchoollevel(equivalenttohighschoolintheUS).Thenumberofpeoplewiththesequalificationsisestimatedat500.ThepoolofexpertiseintheareaofsurveyingandmappingappearstobeadequatetosupportthedevelopmentofaCLRS.However,giventhedramaticchangesinlandlawandtheintroductionofalegalcadastre,additionaltrainingandeducationwillberequiredtoupdatetheskillsandexpertiseofboththeuniversity-andmiddleschool-trainedsurveyors.ThesubstantialsetofmapsthatcurrentlyexistinAlbania,especiallyatlargerscales(1:500-1:10,000),providesavaluablebaseoflandinformationonwhichtobuildaneffectivecadastre.Inadditiontothismapinformation,LRIhasawellorganizedandreferencedarchiveofsurveyrecords,onesetdealingwithcontroldensification(triangulation)andtheotherwithtacheometricsurveys.PerhapsthemostchallengingaspectoftheAlbaniansituationistheminutesizeandfragmentationoflandholdings.Inmanyinstancesvillagershavebeenallocatedbetweenonetofourparcelsofland(uptosevenparcelsareallowedbylaw).Theseindividualparcelsmaybeseveralkilometersapartandinvolveagriculturallandaswellaspastureandlandcontainingolivetrees(definedintermsofthenumberoftrees).Fromasurveyingandmappingperspectivethisfragmentationpresentsacomplexenvironmentinwhichtoidentifycost-effectivesolutionsforthecreationofCLRS.3DESCRIPTIONOFGPSMETHODOLOGYTheGPSmethodologytestedandimplementedinAlbaniautilizedthetechniqueknownas'DifferentialPseudo_RangePositioning'.AminimumoftwoGPSreceiversarerequiredforthistechnique.The'reference'or'base'receiveroccupiesaknowngeodeticcontrolmonumentandthe'remote'or'rover'receiverisusedtooccupyparcelcorners.Thedatacollectedatthereferencereceiverareusedtocomputecorrections(?X,?Y,?Z)tothepseudo_rangemeasurements.Thesedifferentialcorrectionsarethenapplieddirectlytotheremotereceiverduringpost_processing.Themagnitudesofthesecorrectionsarecommontobothunits,providedthatthedistancebetweenthereferencereceiverandremoteunitisnottoogreat,Thetechniqueiscapableofyieldingsub_meteraccuracypositionsfortheparcelcorners.ThemethodologywastestedusingaTrimblePathfinderPROXLasaroverreceiverandasinglefrequencyTrimble4000SEasthereferencereceiver.Thetechniquehasthefollowingadvantages:ImplementationisrelativelysimpleObservationaltechniqueisrobust,thereforerequiringminimaltrainingOnlyonebasestationisrequiredtosupportmultipleroverunits(productivitycanthenbesignificantlyincreasedatarelativelylowcost)Nocoordinationisrequiredbetweenroverunits(fieldcrewscanthereforeoperateindependentlyofeachother)Occupationtimesareshort(30seconds) Ageneraldescriptionofthemethodologyisoutlinedbelowintermsofthefollowingfourcategories:officeplanningandpreparation,fieldprocedures,post_processing,andgeodeticconsiderations.4OfficePlanningandPreparation4.1SatelliteCoverageComprehensiveplanningandorganizationisanessentialpartoftheGPSmethodology.Therefore,priortothesurvey,thesatellitecoveragemustbeevaluatedintheareaofinterestforthegiventimeperiod.Recentephemerisdataarerequired,whichdescribethemostup-to-datecomputedorbitalparametersofthesatelliteconstellation.TheephemerisdataareobtainedbyutilizingaGPSreceivertocollectdatafromatleastonesatelliteforapproximately15minutes.Thisensuresthatthefullnavigationmessageisobtained.Thecollecteddataaredownloadedtoapersonalcomputer(PC).Themissionplanningsoftware(e.g.TRIMBLEQuickPlan),isusedtogenerateanumberofsatellitevisibilitygraphsandreports.Thegraphsdepicting'NumberofSatellites'and'PDOP'offeraconvenientmeansofquicklyassessingwhethersufficientsatellitecoverageisavailable,i.e.aminimumof4satellitesandlowPDOPvalues.PDOPisanindicatorofthegeometricstrengthofthesatelliteconstellation.4.2CreationofaDataDictionaryAdatadictionaryisacatalogofinformationaboutthedefinition,structureandusageofthedata.Itisusedtostructureandguidethedatacollectionprocess.Eachdictionaryconsistsofalistoffeatures,alistofattributesforeachfeature,andalistofvaluesforeachattribute.Forexampleinparcelmapping,asinglefeature'parcelcorner'wasdeemedadequateinthetests.Attributessuchas'parcelid','date'and'time'werealsoincluded.Thetestsinurbanareasrequiredamoredetaileddictionary(includingfeaturessuchas'powerpole','buildingCorner','clofroad','concretebunker','fencecorner',etc).Oncethedatadictionaryhasbeencreated,itisuploadedtothedataloggerforsubsequentuseinthefield.4.3BaseReceiverConfigurationAchievingsub_meteraccuracywithGPSreceiverssuchasthePathfinderProXLisonlypossibleunderspecificoperationalconditions.Theseparameters(e.g.logginginterval,elevationmask,PDOPmask,andSNR(SignaltoNoiseRatio)mask)canbeconfiguredinthereceiverpriortomeasurement.Theloggingintervalspecifiestheregularitywithwhichpositionsarestoredwithinthereceiver.Theamountofdatathatcanbecollectedisrestrictedbythesizeoftheinternalmemorywithinthereceiver.Anintervalof5secondsprovidesabalancebetweenthevolumeofdatagenerated,andtheoccupationtimerequiredbytheroverateachpoint.Theelevationmaskshouldbesetat10toensurethatsatellitestooclosetothehorizonareexcluded,sinceatmosphericeffectsmayresultinsignaldegradation.ThePDOPmaskissettoavalueof8toensurethatdataarecollectedonlywhenafavorablesatelliteconstellationexists.TheSNRratioprovidesameasureofthestrengthofthesignalbeingreceived.AnSNRratiobelow4shouldbeavoided,asthislowsignalstrengthwilladverselyaffectthepositionalaccuracy.4.4RoverReceiverConfigurationTheroverreceivershouldbeconfiguredinthesamewayasthebasereceiver,withthefollowingexceptions.Arequirementofthedifferentialcorrectionprocessisthattherovercollectasubsetofthesatellitesbeingtrackedatthebasestation.Theelevationmask(150),PDOPmask(6),andSNRmask(6)valuesarethereforesettobemorestringentfortheroverreceiver.AlthoughthePathfinderProXLyieldssub_meteraccuracyonasecond_by_secondbasis,itisadvisabletocollectseveralpositions.Thesepositionsarethenaveragedafterdifferentialcorrectiontoyieldamorereliableposition.Theminimumnumberofpositionsshouldbe6,thereforerequiringeachparcel(orbuilding)cornertobeoccupiedfor30seconds.5FieldProcedure5.1ReconnaissanceAthoroughreconnaissanceisanessentialpartofthefieldworkifefficiencyandproductivityaretobemaximized.Thisappliestoallsurveyingtechniques,butisespeciallytrueforGPSsurveying.Reconnaissanceisrequiredinthefirstinstancetoidentifysuitableexistinggeodeticcontrolpointsinthevicinity.Theselectedcontrolpointshouldbeaccessible,preferablybyvehicle,andshouldhaveanopenhorizon.Secondly,theareatobemappedmustbeidentifiedandsketchesofthefieldsshouldbedrawntofacilitateparcel-levelsketchesdrawnduringthemeasurementprocess.Theseproceduresenablethemeasurementprocesstobeoptimizedandtheresultstobeorganizedinalogicalfashion.5.2BaseReceiverSet_upThebasereceivercaneitherbesetupatacontinuouslyoperatedcentralbasestationoratarecoveredcontrolpointinthevicinityofthesurvey.Theheightoftheantennamustbemeasuredandrecordedinafieldbook,togetherwithotherrelevantdata(e.g.thestationname,thedate,thetime,weatherconditions).Careshouldbetakentoensurethatthebasestationiscollectingdatapriortoanyroverreceivers,sinceonlysimultaneousdatabetweenbaseandroverreceiversmaysubsequentlybedifferentiallycorrected.Ideallybasereceiversshouldbesetupatbothacentralbasestationandatacontrolpointinthevicinityofthesurvey(oratasecondcentralizedbasestation).Thisprovidesavaluablecheckonthemeasurementstakenandalsoactsasaback-upshouldoneofthereceiversdevelopproblemsorlosepower.Intheeventthatasecondbasereceiverisregardedastoocostly,itisimportanttointroduceothermeanofcheckingtheGPSresults(e.g.checkingagainstlargescalemapsshowingsomeofthemeasuredfeatures)5.3DataCollectionwithRoverReceiverTheroverreceiver(PathfinderProXL)isenclosedinabackpack,theantennaismountedonarangepole,andthedatacollectorheldbytheoperator.Thisarrangementiswell_suitedtothemobilityrequiredforcadastralsurveying.Themeasurementprocesstheninvolvestheidentificationofeachparcelcornerbythevillagecommunityleader/elder,thecollectionofGPSdataateachpoint(30seconds),andtheannotationofafieldsketch.5.4FieldSketchesFieldsketchesareanessentialpartofthedatacollectionprocedureandconstitutevaluableboundaryevidence.SinceGPSmeasurespointpositions,itisnecessaryinthepost_processingstagetoconnectthesepointstodelineatetheboundarylinestobeshownonthecadastralmap.Itisthereforeimperativethatgoodnotesbemaintainedinthefieldtoallowthereliablegenerationofthecadastralmap,preferablybyapartynotinvolvedinthedatacollectionprocess.Thesketchshoulddepictasclearlyaspossiblethepointname,monumentdescriptions,theboundarylinesasdeterminedinthefield,anyparcelidentificationnumbers,andotherrelevantfieldfeatures.Inthetestsconducted(seenextsection)thisoftenprovedtobethemostchallengingpartofthefieldwork.6Post_processingAttheendofeachdays'work,thedatashouldbedownloadedtothePCandarchivedonaremovablediskettepriortoanyprocessing.Thisensuresthataback_upcopyofallrawdataismaintainedforsecurityreasons.Thedifferentialcorrectionprocessmaybedividedintothefollowingsteps:(1)Specifyandpreparethebasedatafile(s)(2)Enterthereferencecoordinatesofthebasestation(3)Specifyandpreparetheroverdatafile(s)(4)Differentiallycorrectthedata(5)Transformtheresultstolocaldatum.ThesestepsareexecutedasfunctionswithinthePFINDERsoftware.AlldatacollectedandstoredinthereceiverrelatetotheWGS84referenceellipsoid.ThedatashouldbeprocessedonWGS84andconvertedtothelocaldatumonceprocessinghasbeencompleted(seesectionGeodeticConsiderationsformoredetails).ThereferencecoordinatesenteredforthebasestationshouldrelatetotheWGS84ellipsoid.ItmaybenecessarytoobtainthesecoordinatesbytransformingthepositionfromthelocaldatumtoWGS84.Extremecareshouldbeexercisedinthetransformationandsubsequententeringofthesecoordinates,sinceanyerrorinthebasereferencepositionwillbereflectedinsimilarmagnitudeinthecoordinatesoftheparcelcorners.Thedifferentiallycorrectedroverpositionsandtheattributedatacompiledinthedataloggermustbeconvertedtoaformatthatconformswiththemappingsoftware.GenerallyAUTOCADoroneofthemorepopularGIS'(e.g.ArcInfo)willbeusedtomapandmanagetheparceldatabase.PFINDERallowsforconversionintoanumberofcommonformatsforexportingthedatatodifferentmappingandGISpackages.7MapProductionInordertoprovideacleardescriptionofthelandparcelsforregistrationandcadastralpurposes,itisnecessarytogenerateacadastralmapshowingallparcelsinajurisdiction.Thiscadastralmapservesasalegaldescriptionforallregisteredparcels.Metesandboundsdescriptionsarenotregardedasanadequatemethodofdescribinglandparcels.ThecadastralmaporcadastraloverlayalsorepresentsthepropertylayerinamultipurposeLIS/GISandassuchmustbecapableofbeingintegratedwithotherlayersofinformationsuchasnaturalresources,infrastructureandsocio-economicthemes.Thecomputer_aideddrawingsoftware(AUTOCADversion11)wasutilizedduringtestsconductedinAlbaniafortheproductionofthecadastralmap.Itshouldbenotedthattheproductionofareliablerepresentationofthedataishighlydependentuponthecompilationofcomprehensivesketchesduringthedatacollectionprocess.8GeodeticConsiderationsinAlbaniaTheuseofGPStechniqueswithinAlbaniaraisessomeimportantgeodeticissues.Aswasmentionedbefore,allGPSdataarerelatedbydefinitiontotheWorldGeodeticSystemof1984(WGS84).Thissystemisanearth_centered,earth_fixed3_dimensionalcoordinatesystem,withanellipsoidwhichbestapproximatesthesurfaceoftheearthasawhole.ThelocalgeodeticdatumpresentlyinuseinAlbaniaisbasedupontheKrassowskyellipsoid.TheAlbaniandatumisthereforebaseduponalocallybest-fittingellipsoid.Therelationshipbetweenthelocalellipsoidandglobalgeocentricreferencesystems,suchasWGS84,isthereforenoteasilydeterminable,makingaccuratetransformationsbetweenthesesystemsdifficulttoachieve.FinalcorrectedpositionsmaybetransformedontothelocaldatuminAlbaniausingtheappropriatetransformationroutines.ThisapproachalsorequiresthatthereferencestationcoordinatesbeknownintheWGS84system.9RESULTSResultsofthecontrolledtestingontheeffectofbaselinedistanceshowedthatingeneralanaccuracyofaround1metercanbeachieveduptodistancesof135kilometers.Atadistanceof135kilometers1positionfellmorethan1.4metersfromthetruevalue,while6positionsfellbetween1and1.4meters.Whilemostofthemeasurementsfallwithintherequiredaccuracylimit,theseoutliersaregroundsforsomeconcernandtheireliminationwillbepartoftheresearchgoalinthenextphase.Figure1summarizesthemean,minimumandmaximumerrorsforthefivebaselinedistancesthatweretested.TheresultsindicatethatminimaldensificationingeodeticcontrolwillberequiredtosupporttherecommendedGPSmethodology.AscanbeseenonthemapofAlbaniainFigure2,asinglebasestationinTirana(e.g.ontheroofoftheLRIbuilding)couldservealmosttheentirecountry.Thisimpliesasignificantsavinginresourcesandtimeandallowsgreatercontroloverthebasestation.Theresultsofthefieldtestswereveryencouragingandshowedthatthismethodologycanbeemployedveryeffectively.Table1belowdemonstratestheproductivitylevelsachievedintheurbanandruraltestsconductedinAlbania.Thistimereflectsmeasurementtimeonlyanddoesnottakeintoaccounttimespentonadjudicatingparcelboundaries.CONCLUSIONSThetestsconductedattheUniversityofFloridashowedthatmeterlevelaccuracyisachievableevenwhenthebaselinedistancebetweenreferencestationandroverisaslongas135kilometers(seeFigure1).Thismeansthatformostcadastralsurveyingpurposesitisnotnecessarytoinvestinanexpensiveandtimeconsumingcontroldensificationexercisepriortoparcelsurveyingandmapping.PreliminarycomparisonswiththetraditionalsurveyingandmappingapproachshowthattheGPSmethodologycanbesignificantlymoreproductivebothintheofficeandfield.Furthermore,itdoesnotdependonexistingmapsbeingavailableandprovidesdatainadigitalformatwhichcaneasilybetransferredtoacomputerizedmappingsystemorGIS.Giventhelackofmonumentationandthetemporarynatureoftheindividualparcelboundar