From 96330653bffeadbf14159380ce2253e5dda47780 Mon Sep 17 00:00:00 2001
From: Alessandro Cerioni IntroductionThe applied corrections are always the result of a complex process, involving different territory actors, until the decision is made to integrate them into the land register. In addition, land register models comes with an additional constraint linked to political decisions. Indeed, the land register models are the result of a political mission conducted under federal laws making these models of high importance and requiring constant care. We show in this research project how differences detection tool [1] of the STDL 4D framework can be used to emphasize and analyze these corrections along the time dimension.
In addition to the constant updates of the models, changes in the reference frame can also lead to large-scale corrections of the land register models. These global corrections are then made even more complex by the federal laws that impose a high degree of correctness and accuracy.
In the context of the introduction of the new reference frame DM.flex [2] for the Swiss land register, being able to assess the applied changes on the geographical model appear as an important aspect. Indeed, changing the reference frame for the land register models is a long and complex technical process that can be error prompt. We also show in this research project how the difference detection algorithm can be helpful to assess and verify the performed corrections.
-In this research project, the difference detection algorithm implemented in the STDL 4D framework is applied on INTERLIS data containing the official land register models of different Swiss Canton. As introduced, two main directions are considered for the difference detection algorithm :
Through the first direction, the difference detection algorithm is presented. Considering the difference models it allows computing, it is shown how such model are able to extract information in between the models in order to emphasize the ability to represent, and then, to verify the evolution of the land register models.
The second direction focuses on demonstrating that difference models are a helpful representation of the large-scale corrections that can be applied to land register during reference frame modification and how they can be used as a tool to assess the modifications and to help to fulfil the complex task of the verification of the corrected models.
-For the first research direction, the land register models of the Thurgau Kanton are considered. They are selected in order to have a small temporal distance allowing to focus on a small amount of well-defined differences :
This first section focuses on short-term differences to show how difference models work and how they are able to represent the modifications extracted out of the two compared models. The following images give an illustration of the considered dataset, which are the land register models of Thurgau Kanton :
One can see how difference models can be used to track down modifications brought to the land register in a simple manner, while keeping the information of the unchanged elements between the two compared models. This demonstrates that information that exists between models can be extracted and represented for further users or automated processes. In addition, such difference models can be computed at any scale, considering small area up to the whole countries.
-On the previous section, the difference models are computed using two models only separated of a few days, containing only a small amount of clear and simple modifications. This section focuses on detecting differences on larger models, separated by several years. In this case, the land register of the Canton of Geneva is considered :
Typically the swimming pool register is updated either by taking building/demolition permits into account, or by manually checking its multiple records (4000+ to date) against aerial images, which is quite a long and tedious task. Exploring the opportunity of leveraging Machine Learning to help domain experts in such an otherwise tedious tasks was one of the main motivations behind this study. As such, no prior requirements/expectations were set by the recipients.
The study was autonomously conducted by the STDL team, using Open Source software and Open Data published by the Canton of Geneva. Domain experts were asked for feedback only at a later stage. In the following, details are provided regarding the various steps we followed. We refer the reader to this page for a thorough description of the generic STDL Object Detection Framework.
-Several steps are required to set the stage for object detection and eventually reach the goal of obtaining - ideally - even more than decent results. Despite the linear presentation that the reader will find here-below, multiple back-and-forths are actually required, especially through steps 2-4.
As the ground-truth data we used turned out not to be 100% accurate, the responsibility for mismatching predictions has to be shared between ground-truth data and the predictive model, at least in some cases. In a more ideal setting, ground-truth data would be 100% accurate and differences between a given metric (precision, recall, \(F_1\) score) and 100% should be imputed to the model.
-All the predictions having a score \(\geq\) 5% obtained by our best model were exported to Shapefile and shared with the experts in charge of the cadastre of the Canton of Geneva, who carried out a thorough evaluation. By checking predictions against the swimming pool register as well as aerial images, it was empirically found that the threshold on the minimum score (= thr
) should be set as high as 97%, in order not to have too many false positives to deal with. In spite of such a high threshold, 562 potentially new objects were detected (over 4652 objects which were known when this study started), of which:
The analysis reported in this document confirms the opportunity of using state-of-the-art Deep Learning approaches to assist experts in some of their tasks, in this case that of keeping the cadastre up to date. Not only the opportunity was explored and actually confirmed, but valuable results were also produced, leading to the detection of previously unknown objects. At the same time, our study also shows how essential domain expertise still remains, despite the usage of such advanced methods.
As a concluding remark, let us note that our predictive model may be further improved. In particular, it may be rendered less prone to false positives, for instance by:
diff --git a/PROJ-HETRES/images/F17A_all_VarImp.tif b/PROJ-HETRES/images/F17A_all_VarImp.tif new file mode 100644 index 0000000000000000000000000000000000000000..3e1988e84e0a457fd235b542c1525bfe07eabfa1 GIT binary patch literal 3000192 zcmeF)y>9HhnkeWMOfgJ43qGZfYXlYlbb|e8%q*rmXZUY%aC5(`k*Y
zFuEGue6x>%a&R3NE+&Umvi@d!FD~9D@{3W<(0x2-)7>D4B4?PmITDxzh7Y_S{yv$|
z#P|V_KBuR>a8Z?? (uwPgVo(y|YwYXn$D
zYm}(7EWj#S_Mvo*0IO(?5_O&;z~X!g`~C)HA?@#)jz1$-(RlOyjmRq6-!&b7My#Uo
z=8U*ffW^5IifYROETm;0O4kUmiq@AT19A}@x0`LT?M??i&$51a`;vp~)K7b&zO9sM{2n6rDnB+Xy0NNlr{o}j00IbX
zN1)idw=*qff&c;w0(S^07kZ~C2;2eLg~OVRv3HK5HI?G=R5h2{Q}D0v-$`5jzkbn2
z=kY;#=u-3IV|6?H_Qzks3H)_xqE)`6kHO^r(}*(8`HR-kSAGOP{rdsU%s&(0pR)4i
zKmY**o+=<)x8JCrI+tw@o^NwE&+m?1-8>gMcxeHNrCxgeFEROhAnSWRzE1BSlGX?~
z?*k!qo<7wwZN$0MYKBg}o%)do`}Do^lj~_JHja4~ze~-ZgS6&^cwhT)8-D0G^!sJ%
zBHs{t{pTn6Q~d4%`j@z*OcDVE5O}13Y@Da_S-1VU-7##f`Ww8$OKRCZoLkr?p0ncb
zVbC^bxo3oJJa5wODT`JJf4!s}$L;%%Jbn5`0D&0+d27y;kbO6S$0Pe~cVXH^HQmss
zt=_iu6m1t3eTS)n&&z4;@;e{TOHt8PYM#D^rrOG8kUJxV00IacRzP>o<&81an8Ik?
zMcq@En433WO}Uym9
*qdq%1;iQpFI3??HL^b1Q0*~0R#|0;MoE*5qfy$?mm?gpTWmZ)VS;^!cU*HDW1{0
zCQXa;dw8ZV?X<{+#F{*Rgh_=?r