Ciao Fausto e Biagio.
Sì, è vero quello dice Biagio, avevo già scoperto anch'io la causa dello spostamento della base GPS e infatti nel mio nuovo libro gli ho dedicato un paragrafo specifico nel capitolo intitolato
I rischi nel valutare i risultati del calcolo di Pregeo nel quale ho esaminato tutte le "stranezze" del calcolo di Pregeo. Non l'ho riportato qui su Geolive perché, come avrete visto, anche questo topic era stato inquinato dai soliti noti motivati solo dal rancore personale.
La questione è questa: Pregeo calcola sempre e comunque qualsiasi rilievo (sia GPS che TS che misto) come una "rete", sia in presenza dei PF che in loro assenza. Poi questa rete la calcola come ha descritto Biagio.
Ma quali punti include Pregeo nella sua "rete"? C'è da divertirsi a scoprirlo.
1) Innanzi tutto il punto di emanazione del rilievo, quindi la prima stazione TS o la base GPS.
2) Poi inserisce sempre e comunque il primo punto che l'utente (ignaro) inserisce (casualmente) sulla prima riga riga 2 che segue la riga 1 (o 1-6) del punto di emanazione del rilievo. Questa è la causa, ad esempio, degli sqm ed ellissi abnormi se per caso tale primo punto cade vicino alla base.
3) Se ci sono i PF, questi ovviamente fanno parte della rete, ma se anche non ci sono ... non fa niente.
Oltre a questi punti, poi Pregeo nella rete ne inserisce altri "a sua discrezione". Ad esempio:
4) Prendiamo un rilievo GPS nel quale si sono rilevati alcuni spigoli di fabbricati per intersezione, cioè con due punti GPS vicini allo spigolo e le rispettive distanze a quest'ultimo. In questo caso nella "rete" Pregeo inserisce anche tutti i punti GPS generatori degli allineamenti più anche i punti determinati dagli allineamenti stessi. In pratica, Pregeo considera "iperdeterminati" questi punti, il che è ovviamente scorretto perché non possono costituire un'iperdeterminazione le distanze prese con il disto o la cordella metrica allo spigolo. Ho analizzato questa casistica nel libro, vi riporto qui il brano in PDF:
Sqm_da_zero_ad_abnormi.pdf 5) Poi Pregeo include nella "rete" anche altre iperdeterminazioni. Esempio, prendiamo questo libretto (rilievo reale):
1|0024|4492042.870,654743.440,4465615.550|0.000|
6|L2|21012022-09:39|21012022-09:39|RTK|PDOP=3|
2|2004|5660.272,12554.628,-7129.815|0.000206868,0.000040136,0.000119062,0.000066681,0.000018592,0.000167719|PDOP=1|0.000|
2|2001|5612.352,12446.644,-7084.414|0.000120488,0.000020843,0.000082753,0.000036665,0.000011543,0.000120312|PDOP=1|0.000|
2|2007|5495.278,13313.437,-7074.985|0.000315994,0.000046169,0.000226784,0.000078707,0.000016094,0.000301960|PDOP=1|0.000|
Qui nella "rete" ci vanno soltanto la base GPS 0024 e il primo punto 2004 che la segue nel libretto, con questi risultati:
nome nord sqm est sqm semiasseMax semiasseMin inclinazione
0024 -0.211 +/-0.003 0.238 +/-0.003 0.004 0.000 153.850
2004 -10280.799 +/-0.003 11606.122 +/-0.003 0.004 0.000 153.850
Cioè la base è spostata "solo" di 21 e 23 cm.
Ora consideriamo la versione effettiva di questo libretto, nella quale il tecnico, per scrupolo, ha registrato più volte la baseline dei punti 2004 e 2007:
1|0024|4492042.870,654743.440,4465615.550|0.000|[WGS84-ETRF2000]|
6|L2|21012022-13:00|21012022-14:00|RTK|PDOP=1|
2|2001|5613.619,12446.832,-7083.149|0.000120,0.000021,0.000083,0.000037,0.000012,0.000120|PDOP=1|1.800|
2|2002|5613.618,12446.831,-7083.149|0.000119,0.000021,0.000082,0.000037,0.000011,0.000119|PDOP=1|1.800|
2|2003|5661.537,12554.817,-7128.551|0.000208,0.000040,0.000120,0.000067,0.000019,0.000169|PDOP=1|1.800|
2|2004|5661.539,12554.816,-7128.550|0.000207,0.000040,0.000119,0.000067,0.000019,0.000168|PDOP=1|1.800|
2|2005|5661.539,12554.817,-7128.551|0.000204,0.000039,0.000118,0.000066,0.000018,0.000166|PDOP=1|1.800|
2|2004|5661.536,12554.810,-7128.556|0.000171,0.000031,0.000097,0.000055,0.000011,0.000139|PDOP=1|1.800|
2|2006|5661.534,12554.808,-7128.554|0.000175,0.000032,0.000099,0.000056,0.000011,0.000143|PDOP=1|1.800|
2|2007|5496.545,13313.625,-7073.720|0.000316,0.000046,0.000227,0.000079,0.000016,0.000302|PDOP=1|1.800|
2|2007|5496.563,13313.627,-7073.708|0.000257,0.000037,0.000189,0.000064,0.000014,0.000252|PDOP=1|1.800|
2|2007|5496.589,13313.626,-7073.687|0.000212,0.000029,0.000154,0.000051,0.000009,0.000204|PDOP=1|1.800|
2|2008|5496.599,13313.630,-7073.679|0.000198,0.000030,0.000143,0.000047,0.000010,0.000191|PDOP=1|1.800|
2|2007|5496.610,13313.634,-7073.672|0.000185,0.000028,0.000132,0.000045,0.000009,0.000177|PDOP=1|1.800|
2|2009|5496.622,13313.636,-7073.667|0.000178,0.000026,0.000123,0.000044,0.000007,0.000165|PDOP=1|1.800|
2|2010|5496.605,13313.634,-7073.689|0.000159,0.000020,0.000094,0.000040,0.000004,0.000123|PDOP=1|1.800|
2|2007|5496.607,13313.634,-7073.692|0.000158,0.000021,0.000092,0.000039,0.000006,0.000119|PDOP=1|1.800|
In questo caso nella "rete" ci finiscono anche questi due punti 2004 e 2007, anche se di fatto le baseline multiple comportano variazioni millimetriche, che sono tuttavia sufficienti a spostare la base a 31 e 36 cm:
Punti della Rete
nome nord sqm est sqm semiasseMax semiasseMin inclinazione
0024 -0.312 +/-0.001 0.361 +/-0.002 0.002 0.000 152.832
2001 -10204.818 +/-0.004 11506.878 +/-0.004 0.004 0.004 153.060
2004 -10281.381 +/-0.004 11606.790 +/-0.004 0.004 0.003 153.301
2007 -10204.563 +/-0.003 12381.430 +/-0.003 0.003 0.003 157.591
Se invece rinominiamo le ripetizioni dei punti 2004 e 2007...:
1|0024|4492042.870,654743.440,4465615.550|0.000|[WGS84-ETRF2000]|
6|L2|21012022-13:00|21012022-14:00|RTK|PDOP=1|
2|2001|5613.619,12446.832,-7083.149|0.000120,0.000021,0.000083,0.000037,0.000012,0.000120|PDOP=1|1.800|
2|2002|5613.618,12446.831,-7083.149|0.000119,0.000021,0.000082,0.000037,0.000011,0.000119|PDOP=1|1.800|
2|2003|5661.537,12554.817,-7128.551|0.000208,0.000040,0.000120,0.000067,0.000019,0.000169|PDOP=1|1.800|
2|2004|5661.539,12554.816,-7128.550|0.000207,0.000040,0.000119,0.000067,0.000019,0.000168|PDOP=1|1.800|
2|2005|5661.539,12554.817,-7128.551|0.000204,0.000039,0.000118,0.000066,0.000018,0.000166|PDOP=1|1.800|
2|3004|5661.536,12554.810,-7128.556|0.000171,0.000031,0.000097,0.000055,0.000011,0.000139|PDOP=1|1.800|
2|2006|5661.534,12554.808,-7128.554|0.000175,0.000032,0.000099,0.000056,0.000011,0.000143|PDOP=1|1.800|
2|2007|5496.545,13313.625,-7073.720|0.000316,0.000046,0.000227,0.000079,0.000016,0.000302|PDOP=1|1.800|
2|3007|5496.563,13313.627,-7073.708|0.000257,0.000037,0.000189,0.000064,0.000014,0.000252|PDOP=1|1.800|
2|4007|5496.589,13313.626,-7073.687|0.000212,0.000029,0.000154,0.000051,0.000009,0.000204|PDOP=1|1.800|
2|2008|5496.599,13313.630,-7073.679|0.000198,0.000030,0.000143,0.000047,0.000010,0.000191|PDOP=1|1.800|
2|5007|5496.610,13313.634,-7073.672|0.000185,0.000028,0.000132,0.000045,0.000009,0.000177|PDOP=1|1.800|
2|2009|5496.622,13313.636,-7073.667|0.000178,0.000026,0.000123,0.000044,0.000007,0.000165|PDOP=1|1.800|
2|2010|5496.605,13313.634,-7073.689|0.000159,0.000020,0.000094,0.000040,0.000004,0.000123|PDOP=1|1.800|
2|6077|5496.607,13313.634,-7073.692|0.000158,0.000021,0.000092,0.000039,0.000006,0.000119|PDOP=1|1.800|
La "rete" torna ad essere quella classica (base + primo punto casuale) e la base torna a spostarsi solo di 20 e 22 cm:
Punti della Rete
nome nord sqm est sqm semiasseMax semiasseMin inclinazione
0024 -0.201 +/-0.002 0.226 +/-0.002 0.003 0.000 153.813
2001 -10204.710 +/-0.002 11506.741 +/-0.002 0.003 0.000 153.813
Punti di Dettaglio
2002 -10204.709 +/-0.006 11506.740 +/-0.006 0.008 0.003 48.051
2003 -10281.271 +/-0.008 11606.657 +/-0.008 0.011 0.003 48.742
2004 -10281.271 +/-0.008 11606.656 +/-0.008 0.011 0.003 48.742
2005 -10281.272 +/-0.008 11606.657 +/-0.008 0.011 0.003 48.706
3004 -10281.273 +/-0.007 11606.650 +/-0.008 0.010 0.003 48.497
2006 -10281.270 +/-0.008 11606.649 +/-0.008 0.010 0.003 48.502
2007 -10204.444 +/-0.009 12381.294 +/-0.009 0.012 0.003 48.689
3007 -10204.448 +/-0.008 12381.293 +/-0.008 0.011 0.003 48.739
4007 -10204.451 +/-0.007 12381.289 +/-0.008 0.010 0.003 48.711
2008 -10204.453 +/-0.007 12381.291 +/-0.007 0.010 0.003 48.648
5007 -10204.456 +/-0.007 12381.293 +/-0.007 0.009 0.003 48.662
2009 -10204.461 +/-0.007 12381.294 +/-0.007 0.009 0.003 48.684
2010 -10204.465 +/-0.007 12381.294 +/-0.007 0.009 0.003 49.164
6077 -10204.468 +/-0.007 12381.294 +/-0.007 0.009 0.003 49.306
Questo è quanto ho scoperto finora sul calcolo di Pregeo (nel libro ho spiegato in dettaglio tutte le casistiche), ma non è detto che non emergano altre situazioni del libretto che creino una "rete" ancora diversa, con risultati altrettanto diversi ma ...
a parità di rilievo.
Buon Ferragosto.
geom. Gianni Rossi
Responsabile corsi online del Collegio Geometri e G.L. di Padova
cell. 3202896417
Email: gianni.rossi@co**************
www.co************** www.to************