PE&RS December 2018 Full - page 759

PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING December 2018 759
the software published by the U.S. National Geodetic Survey
(NGS) and to train some of their geodetic staff in the opera-
tion of that software. I had a brand-new laptop computer with
me; a new dual-floppy drive Zenith Z-181 and I demonstrat-
ed some of the NGS “MTEN” software to the Director while
I spoke. The Director said my proposal had merit and he
agreed to the “trade,” but he said it would take several days
to amass the data I wanted. He inquired if I would be around
that long, and I replied that I was on a working holiday with
my rather large family and I expected to stay for as long as
it took to acquire the data. I spent the remainder of the week
downloading and installing the NGS software into the DCN
computers and training some of their geodesists. One after-
noon when I returned to the hotel, I was summoned by the
desk clerk and asked if everything was all right. I then asked,
“Why the question,” and he told me that the Secret Police had
been there that day and had inquired about my family. I then
asked, “what happened?” Seems that they took the two mem-
bers of the Secret Police outside near the pool, pointed out
my family, and watched them count my children. The desk
clerk said police seemed satisfied and just left without anoth-
er word. The next day I went to the DCN, nothing was said
about the incident and I did not ask. That weekend was spent
sightseeing in Caracas and nearby towns in the Andes; the
following Monday I met with the retired Dr. Adolfo Romero,
father of the PSAD56. The interview was fascinating and Dr.
Romero preferred to use his English rather than put up with
my Spanish. The datum shift methods used by the DCN were
Helmert transformations and were localized to metropolitan
Caracas for cadastral changes from Loma Quintana 1911 to
PSAD56. On Tuesday, 23 December 1986, I was successful in
obtaining the Trig List coordinates on the last working day of
the year for the DCN. I telephoned the attorney and happily
informed him that I was not going to need his services and
left Venezuela with my family shortly after that.
The results of the Datum relations subsequently comput-
ed were as follows: From Old Trinidat Datum of 1903 To
PSAD56, ΔX = +84.70 m, ΔY = –180.65 m, ΔZ = +96.90 m,
scale = –17.79x10-6, RX = –7.99˝, RY = +5.66˝, RZ = +25.19˝,
and was based on a solution of 61 collocated stations. From
Loma Quintana Datum of 1911 To PSAD56, ΔX = –43.50
m, ΔY = +96.14 m, ΔZ = –15.18 m, scale = +16.70x10-6, RX =
–1.43˝, RY = –0.65˝, RZ = –0.33˝, and was based on a solution
of 79 collocated stations. From Naparima Datum 1972 To
PSAD56, ΔX = –27.69 m, ΔY = +40.01 m, ΔZ = –17.56 m, scale
= +7.85x10-6, RX = –11.33˝, RY = +4.34˝, RZ = +17.83˝, and
was based on a solution of 61 collocated stations. The treaty
between the High Contracting Parties on “the delimitation of
marine and submarine areas was DONE in the City of Ca-
racas, on the 18th day of the month of April, One Thousand
Nine Hundred and Ninety in duplicate in the English and
Spanish languages, both texts being equally authoritative...
The positions of the aforementioned points have been de-
fined by latitude and longitude of the 1956 Provisional South
American Datum (International ellipsoid 1924).”
“Venezuela, as it has been established in Official gazette
no. 36.653 of date 03-03-99, has a new geodetic network called
SIRGAS-ReGVen (Venezuelan GPS Network), which is a
very precise network.” PATVEN-07 Transformation Param-
eters are From PSAD56 (Canoa) To ReGVen: ΔX = –270.933
m, ΔY = +115.599 m, ΔZ = –380.226 m, scale = –5.108x10-6,
R X = –5.266˝, RY = –1.238˝, RZ = +2.381˝.
Update
The latest public news of “La Cartografia Nacional de Ven-
ezuela” offers statements of work quality, but does not offer
any details of actual work accomplished except for gravimet-
ric observations which are likely the 50-75 year-old relative
gravity network related to the PSAD56:
“The geocentric Network Venezuela (REGVEN) is com-
prised of a set of distributed vertices in the country, physi-
cally represented through permanent monuments or geodesic
marks, whose position is determined with high accuracy. Be-
cause of the need to increase the number of vertices relat-
ing to the global geocentric system, we have been carrying
out various jobs to achieve the densification of REGVEN in a
lower order of accuracy, for which a new classification of the
National Geodetic Control was performed, which is described
below:
1.1. ORDER A: It is represented by those vertices or
stations that belong to the Geocentric Reference System
for the Americas SIRGAS and permanent GNSS stations
are certified by the IGVSB.
1.2. ORDER B: Represented by the vertices measured in
REGVEN REGVEN 95 and 2000 campaigns, as well as
those that it considers appropriate IGVSB whose accura-
cy is greater than about 2 centimeters.
1.3. ORDER C: Those vertices representing densifica-
tion of commands A and / or B of REGVEN, and whose
accuracy is better than or equal to about 5 centimeters.
For this reason has been implemented to establish new
vertices REGVEN order C, as a densification of the com-
mands A and / or B, to increase the number of vertices
distributed throughout the country.
REGVEN densification is the starting point to realize and
promote the development of local geodetic networks, as the
geodesic structure that will give land quality in its physical
component, defined and georeferenced to the national geodet-
ic system.”
More specific news at their website primarily refers to
claimed benefits of socialism.
The contents of this column reflect the views of the author, who is
responsible for the facts and accuracy of the data presented herein.
The contents do not necessarily reflect the official views or policies of
the American Society for Photogrammetry and Remote Sensing and/
or the Louisiana State University Center for GeoInformatics (C4 G).
This column was previously published in PE&RS.