IMPLEMENTATION OF LEGAL DIGITAL CADASTRE IN ISRAEL
Dr. Gershon STEINBERG, Israel
Key words:
INTRODUCTION
The Survey of Israel (SOI), Israel's national surveying and mapping
agency, plans to implement full legal digital cadastre (LDC) in Israel
by 2010. By LDC we mean definition of the cadastral boundaries by
coordinates in a homogenous and accurate geodetic control network..
The ultimate goal is to achieve an accuracy of 5 cm (at 95% confidence
level). The New Survey Regulations of 1998 (Forrai et al., 2000), was
written in order to make sure that this accuracy will be achieved in
every new cadastral project. About 7000 mutation cadastral plans
("re-parcellations") and about 400 registration blocks that
was prepared by the SOI since 1994, also meet this goal. It was
achieved by using combination of GPS horizontal control and EDM, in
the New Israeli Grid (Adler, Papo, 1984). The modern Israeli cadastre
was established in 1920 by the British mandate in Palestine, and was
based on Torrens principles. About 21000 square km of the registered
area (about 5% of the area is not registered yet) are divided into
about 15000 registration blocks, and about 750000 parcels. The area
included in each block sheet changes according to the block's
boundaries and especially according to its scale. The scales are from
1:625 down to 1:50,000. The sheet size is about 60x70 cm. Most of the
sheets are in 1:1,250 and 1:2,500. The accuracy in which the
boundaries are defined is quite heterogeneous as a result of the
survey methods and equipment that were used. The Survey Regulations
for the triangulation and especially for its densification by
traverses that was in use until 1987 was too liberal. For example: a
traverse could be 3000 meters long, with 49 permitted legs (longer
than 60 meters) and the linear miss- closure was 1 to 1500 in urban
area and 1 to 1000 in rural area. There was no hierarchy for the
traverses and there was no limit for the suspension of one traverse on
another, as long as it conformed to the requirements of the permitted
miss-closure. The cadastre was based mainly on the measurement of
boundary marks and other objects, most of which were destroyed with
the fast development of the state of Israel. Until the early
seventies, the cadastral mapping was based on tape (and/or chain)
measurements using the orthogonal (offset) method. It was plotted
without computing the coordinates. The original measurements are kept
in about 30000 "field books". The plotted measurements (on
"field sheets") was taken to the field, where the
"examiner" added direct distances ("fronts")
between the corners of the narrow side of the parcels. These distances
were used as a check to the graphical plotting, and were also used
partly to calculate the area of the parcels by semi-graphic methods.
The area of other parcels was measured graphically, mainly by "planimeter".
Sometimes the examiner has changed the location of several points on
the field sheet without recording the change anywhere else. The field
books and field sheets of quite large area were lost during the
Independence War of Israel. What were kept, were only the registration
block sheets, which are copies of the field sheets on transparent
paper, without written distances on them. Since the introducing of EDM
in the early seventies, the coordinates of the cadastral boundaries
are computed and checked against the direct tape measurements of the
fronts. Also some tens thousands of mutations in the cadastre (called
also "registration plans"), are computed. These are
"islands" of higher local accuracy, but they suffer from the
distortions of the old geodetic network. In order to achieve
homogenous accuracy of 5 cm, we have to reconstruct and measure most
of the boundaries that were already measured in the past. That is an
enormous task, the economic importance of which is doubtful, and the
probability of its implementation is poor. On the other hand, the
present situation in which we do not have digital legal definition of
the cadastral boundaries is not reasonable and is not proper for a
modern state in the new millennium. The situation is very bad once we
understand that there is no unique definition to the boundaries, and
that the possible errors in reconstruction of boundaries might reach
some decimeters. This situation is getting worse with the development
of the country, which involves destruction of old objects that can
still be used for the reconstruction of boundaries. The harder the
reconstruction of boundaries becomes, the more it causes delays in new
measurements and their approval, followed by investment of multiple
economic resources and growing of the possible errors. We also have to
keep in mind that at the same time, the value of the land is growing
constantly. Today we already have many areas in which the value of a
strip of land 5 cm wide and 20 meters long is more than 1000 U.S.$. A
lot of surveys, which contain reconstruction for boundaries, and are
used for building projects, are done in Israel with no necessity for
cadastral mutation plans. Non-reversible facts are actually
established in the area, without the approval of the SOI and without
considering a wide picture of the cadastral connections. It can cause
a situation in which a parcel between two others that were
reconstructed separately would lose a substantial part of its area
while every thing was done legally. Digital legal definition of the
land boundaries would prevent of course all such problems, and it
would dramatically fasten the work and decrease the price of any
measurement for reconstruction of boundaries. Here are some examples
of its influence on our life: A basic condition for approval of
mutation plan in Israel, is its conformity with a detailed municipal
plan. The cadastral layer in those plans is based usually on digitized
graphic material from the registration blocks. This material does not
guarantee the requested suitability and causes in advance inaccurate
municipal plans. Available LDC will be the solution for this problem
and will significantly contribute to acceleration in the preparation
and approval of municipal plans and of cadastral mutation plans. Once
we have LDC we can plan, mark in the field, and check immediately
every building project. Actually, very soon we shall not understand
how we could live without it. The question is how to achieve it
efficiently and in reasonable time. Following are some ideas the
implementation of which will bring us to our goal.
IDEAS FOR IMPLEMENTING LDC
1. Ongoing cadastral projects
By cadastral projects we mean both mutation plans in registered
area and measurements of new registration blocks in unregistered area.
As mentioned above, all the cadastral projects that were prepared by
the SOI (by contracts with private surveyors) since 1994, meet the
accuracy criteria of the LDC. The basic geodetic control for all these
projects were done by GPS measurements, tied mostly to 3rd order
"triangulation" control points that was readjusted to be a
homogeneous accurate horizontal geodetic control, and have coordinates
in the New Israeli Grid (NIG). Since 1996 there is a directive
published by the SOI that every mutation plan containing more than 5
new parcels or larger than 10 dunams (10000 sq. meters) must have
coordinates in the NIG. The need for coordinates was already one of
the regulations in the Ordinance Surveys of 1987, but the change was
the necessity to use the NIG. This demand meant mostly use of GPS
measurements, because of the impossibility to tie the surveys to
control points of the lower order that exist in the field but were not
computed in the NIG, due to the incompetence of its measurements (as
described in the introduction). The new Survey Regulations were
published in July 1998 and every cadastral mutation plan that is
brought to approval at the SOI since January 1999 must be prepared
according to them. In addition to the use of NIG in every cadastral
project, it has to be presented on electromagnetic media, in a special
format of the data, which would enable easy check and almost automatic
storage in the cadastral database .
The annual rate of cadastral projects is about 1200 mutation plans
and 100 new registration blocks, spread over an area of about 100
square kms. There are also intentions to accelerate the work in the
unregistered area in order to finish it by 2010.
2. Legalizing the digitized cadastre of the Israeli Land
Administration
About 92% of the land in Israel, belongs to the state and is
managed by the Israeli Land Administration (ILA). Tenure of these
lands is done through a long term leasing in a variety of ways. The
status of the cadastre in most of the area does not fit its actual
use. In every case of preparing a mutation plan in such an area
according to its real use, or according to new municipal plans and new
development projects, the registered boundaries are canceled and new
boundaries are created instead of them. It means that there is no
importance to the accuracy of the registered boundaries, even when
they are marked in the field. The SOI is completing digitizing and
"stitching" all the registered block sheets of Israel. This
is based on graphic material, and so the accuracy of the product
(called "cadastral GIS"), is changing from some decimeters
(large scale block sheets) to some meters (small scale block sheets).
The ILA is managing a parallel system of the land-use. The idea is to
adopt the inaccurate coordinates of the "cadastral GIS", in
all the places where the ILA is ready for it, and declare these
coordinates as LDC. Boundaries between this area and other kind of
land use (private or long lease in urban area) will be treated as in
the following paragraph 4.Until this treatment (which might take some
time) is completed, we should work according to special restrictions
about how close to the other kind of land-use we can adopt the
cadastral GIS. The adoption will not be done in areas, in which there
are already approved mutation plans with coordinates. An un-prevented
result of this legalization act is a massive change of the parcels
area in the Land Registration Office, so that the area will fit
exactly the coordinates of the boundary framework. Otherwise, the area
of too many parcels will not stand in the permitted tolerance of the
difference between computed and registered area. This result has clear
advantages (no more dealing with discrepancies between registered and
computed area), and it is easy to be done (legally) once the lands
owner (ILA in this case) agrees to do it.
Most of the land of Israel belongs to the category of this
paragraph.
3. Growing skeleton of LDC by every-day building activity
According to the new Survey Regulations, every new mapping,
although not for registration, should be done by the same methods and
accuracy of the Regulations. Survey works involved with reconstruction
and/or measurements of boundaries, take place every day. The idea here
is to collect all this information from the surveyors. Every parcel
that is measured and has coordinates in the NIG, will become a growing
skeleton structure of LDC and will be used as spread islands helping
to anchor other measurements. The availability of the information to
all the surveyors will ease their work near locations of previous work
and will enable them to check their work and be sure it was done
properly.
4. Approximate LDC
As was said in the introduction, it is a huge task to achieve the
desired goal of full accurate LDC. Reconstruction and measurement of
all the cadastral boundaries (even without those detailed in paragraph
1 above) should cost about 500 million US$. The economic importance of
performing this task is doubtful. It is also not realistic for the
surveyors' resources of Israel to fulfill such task within 10 or even
20 years. The solutions described in the first three paragraphs meet
the requested accuracy of 5 cm at a confidence level of 95%. In this
paragraph we bring a solution, which is a reasonable substitute to the
desired product, with the cost of about 10% to 20% of it. This
solution, which we call approximate LDC (ALDC), will be implemented in
the area that was not dealt with in the previous paragraphs. The
solution will be executed in the following way:
- Gathering of all the existing measurements data from the field
books, field sheets, mutation plans, digitized graphic material
(when no other data exist), and the coordinates of the control
points that were used in the measurements. Other sources of
information are the topographic GIS and the orthophoto coverage,
in which one can identify objects that appear in the original
measurements.
- About 5% to 10% of the original control points, or boundary
points, or objects, which exist in the field and are supposed to
be authentic (belong to the original measurement), will be
measured by the combination of GPS and total-stations. When such
details are not found, effort will be made to locate and
reconstruct authentic objects by the use of old air photographs.
Substantial built up fences will be measured too.
- A sophisticated least square adjustment will be done with all
the new measurements of (b) and the old data of (a). The
adjustment will be made with consideration of geometric
information like straight and parallel lines and width of roads as
in (Doytsher, 1981 and 1997).
- The least square adjustment is accompanied by accuracy estimate.
It will give the idea whether we have to measure more objects and
also whether we can adopt substantial fences (which are not
authentic) as if it is authentic. The idea here is to adopt
physical evidence as long as it stands with in the accuracy that
can be achieved, even when we know that it is not exactly in its
original location. In that case another iteration of the
adjustment will be made, including the additional data.
Some experiments and research that were done, see e.g.( Fradkin ,Doytsher,
1997) show that we should expect to get standard deviation (s.d) in
the range of 5 cm to 25 cm. We should not expect to reach low and
homogenous standard deviation everywhere, due to different accuracy of
the original measurements and to different conditions in the field.
The least square adjustment should give us the indications for
improving the results through adding of measurements (when possible),
including the use of old air photographs. The result of the adjustment
is ALDC. The coordinates of the cadastral boundaries (except those of
the authentic ones that were measured), will be considered correct and
legal as long as there is no better contradicting evidence. In every
case of reconstructing boundaries by the data of the ALDC, the
surveyor will have to check for existence of authentic objects that
enable more accurate reconstruction. The searching distance (radius)
for such objects will be derived from the s.d of the adjustment.
Reasonable distance is 25 meters for every 10 cm of s.d . Once
authentic objects are found, they will be measured. Those new
measurements will be added to the observation-equations through a
process of sequential least square adjustment. Every new
reconstruction of boundaries (although when no additional authentic
objects are found, and the reconstruction was based on the ALDC), will
be registered, and will be used in the future as authentic data. The
same rule will be used also with substantial physical boundaries
(fences) that are built in the range of 3 times the s.d , as long as
the "fronts" of such boundaries, as well as the other fronts
(that are not built) between these boundaries will conform to this
criterion .As a matter of fact, this idea is already a long time a
part of the Survey Regulations for "graphic" reconstruction
of boundaries. The rule in this case is to search for original
boundary marks within a radius of 1 meter when the digitized block
sheets are in the scale of 1:1,250 and a radius of 2 meters when the
scale is 1:2,500. There are difficulties with the fact that such
measurements get an official recognition only as an approval of
mutation plans. Now, it will belong to the LDC with every
reconstruction of boundaries, as a part of paragraph c above.
Most of the work and the resources to be invested are in the
category of this paragraph.
SUMMARY
A rough estimate of the cost of the project in Israel is in the
range of 50 to 100 million U.S dollars. About half of the cost is
needed for fieldwork and the other half to office activity. It means
an expense of less than 2$ per capita for the next 10 years. It is a
reasonable price, and there is no doubt about its necessity in the
long run. The LDC will make a revolution with all the surveys that are
connected to planning, building and registration of land. Planning
will be based on available digital cadastral layer. Marking of parcels
for building will be based on available digital material, which can be
used fast and easy in the GPS era. The above is good also for
authorities supervision of building according to the approved plans.
Available LDC will fasten and reduce the cost of preparing, checking
and approval of cadastral mutation plans. The citizens' right for
information includes the information about their most valuable
property, which are their house and land. Available LDC will supply
every one with immediate information about the exact location, shape
and area of their property. Implementing of LDC is the basic condition
for 3 dimensional cadastre, which is in its first steps (Doytsher,
Forrai, Kirschner, 2001). It complies also with the FIG Vision for a
Future Cadastral System- Cadastre 2014 (Kaufmann, Steudler, 1998).
REFERENCES
Adler R. and Papo H., "Change of Projection following
Readjustment" ,The Cartographic Journal, Vol.22, 1984, pp.138-140
Doytsher Y., 1981. "Numerical Processing of Graphical
Cadastral Information", In Proceedings of 16th International
Congress of Surveyors, Montreux, Switzerland, paper 304.5.
Doytsher Y., 1997. "Geometrical and Topological Improvement of
Structures Measured from Photographs", Surveying and Land
Information Systems, Vol. 57(1), pp.11-22.
Doytsher Y., Forrai J., Kirschner G., 2001. "Initiatives to
ward a 3D GIS - Related Multi - Layer Digital Cadastre in
Israel", FIG FWW 2001, Seoul, Korea.
Forrai J., Doytsher Y., Krupnik A., Shoshani U., Meltzer Y.,
Steinberg G., "The New Israeli Regulations for Surveying and
Mapping: Integrating New Technology and Methods with Existing Mapping
Routines ", 2000 (Submitted to the Australian Surveyor).
Fradkin K., Doytsher Y., 1997. "A Method for Establishing an
Accurate Urban Digital cadastre in Israel", 1997 GIS/LIS Annual
Conference, Cincinnati, Ohio, USA (CD proceedings).
Kaufmann J., Steudler D., 1998, Cadaster 2014 - A Vision for a
Future Cadastral System, FIG Commission 7 / working group 1, July 1998
BIOGRAPHICAL NOTE
Dr. Gershon Steinberg, Survey of Israel
Since 1995 Deputy Director General for Geodesy and Cadastral
Surveys
1993-1995 Head, Division of Cadastral Surveys and Geodetic
Computations
1988-1993 Head, Division of Cadastral Surveys
1972-1988 Head, Division of Horizontal and Vertical Geodetic Field
Control
Since 1993 Adjacent senior lecturer in the Technion, Israel Institute
of Technology, Haifa, Israel
Selected papers:
Steinberg G, Papo H, " The Future of Vertical Geodetic Control
" , In Proceedings of "GEODESY AND SURVEYING IN THE FUTURE,
The Importance of Heights" , pp.313-320, Gavle, Sweden, March
1999.
Steinberg G, Papo H, "Ellipsoidal Heights: The Future of Vertical
Geodetic Control", GPS World , February 1998.
Societies:
Israel's delegate to commissions 5 and 7 of FIG.
Rotary International
CONTACT
Dr. Gershon Steinberg
Deputy Director for Geodesy and Cadastral Surveys
Survey of Israel
P.O. Box 14171
61141 Tel Aviv
ISRAEL
Tel. + 972 3 561 5708
Fax + 972 3 623 1806
E-mail: gershon_steinberg@hotmail.com
or forrai@soi.gov.il
15 April 2001
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