GIS data models: how to georeference a farm?

1 GIS data models: how to georeference a farm? Nicola Ferr The spatial characteristics of an are many ways to spatially describe a establishment, construction or, in the case of an open-air farm, any place in which animals are held, kept or handledthe whole area and all infrastructures on it under the control of an operator to perform agricultural or aquaculture activitiesgranularity1 spatialelement>1 spatialelementprimitivepointpolygonscala blesameshapefor wholescalesmulti-scalespatialrepresetnat ionThe spatial characteristics of an objectDefinition: In order to be able to represent an object inside a GIS, we first need to define what we are referring to. Granularity: Granularity is a level of details. Granular objects are those, which are at lowlevel detail in your GISP rimitive: A graphicrepresentation of a locationScalability: Scaleaffects the degree of generalization of features being spatial characteristics of an are many ways to spatially describe a need an information model to represent an object in a GIS software, in order and precisely state requirements to represent the object so that all stakeholders may understand and agree about them, about the design of the system, process, and the tool that will be used to capture the information, multiple solutions also from the economical point of spatial characteristics of an objectWhat is an information model and why do you need one?

2 Information Model provides the frameworkfor organizingyour content so that it can be deliveredand framework assists authors and users in finding what they needOnce you have created an Information Model for your content repository, you will be able to label information in ways that will enhance searchand retrievalInformation modelFrom a geomatics point of view, an information model allows the user to create a representationof how an object looks on a GIS softwareDefinitionSpatial characteristicChoose the primitive and attributesInformation modelDefinition: ..in [..] any place in which animals are held, kept or handled [..][..] spatial information on zones where specific management, restriction or regulative regimes are established [..] establishing a dictionaryof the terminology used giving some examples( photos, drawings) to exemplify the conceptInformation modelSpatial characteristic: to consider only the essential spatial elements that characterize the objectosome element must be ignored ( : silos, farmer house)osome other identified ( : building, shelters, plots).

3 You should choose which is the relevant spatial characteristicof the object according to your : features are often "vague, gradual, or fuzzy"Information modelInformation modelPrimitive & attribute -accuracyAccuracy: Detail with which features are represented (both spatial and properties).Elementsto consider: what you intend doing with the feature grain and extent (scale) costs of capturing and maintaining the featureInformation modelPrimitive & attribute-usageTypical spatial information usage: .. just to produce a simple map of Object inventory Spatial calculation ( : distance, surface) Spatial analysis ( : spatial density, hot spot)Information modelPrimitive & attribute-scale Map scale affects map detail a larger scale map can show more detail than a smaller scale map.

4 Information content is correlated with grainand extentGrain: is the size of the individual units of observation; , the finest unit of managementExtent: isthe spatial domain over which the system is studied and for which data are availableInformation modelPrimitive & attributeGeneralisation vs Abstraction Generalisation: Generalization is the method used in GIS to reduce detail in data (by removing details, a geographic feature become simplified) Abstraction: A simplified idea of a real-world objectInformation modelPrimitive & attributeGeneralisation vs AbstractionWith the abstraction process we simultaneously focus on important characteristicsof geographic content, structure, and process while temporarily suppressing certain details, rather than on the elimination or deletion of details (generalisation).

5 Information modelPrimitive & attribute-costs As scale gets larger, accuracy gets better, and cost increasesDecide on a map accuracy that meets your requirements and that you can affordTake home message # 1 Before to start to collect geospatial data you need to define (clearly) an information modelTake home message # 2An information model is based on:Take home message # 3 Scale, cost, and accuracyare inseparably intertwinedContent accuracy: imprecise definitionSpatial accuracy: incoherent spatial representationAttribute accuracy: wrong proprietiesTake home message # 4 Abstraction and generalization are fundamental to define the way to represent an ALWAYS the costs for data production and modelQuestions?Information model practicalexampleGoal: to georeference the farms of an area in Italy to produce a farm distribution mapStep1:DefinitionI do not need to provide a farm definition that is suitable for everycircumstance inside and outside the veterinary domain, I need a definition that is specifically thought for the spatialelement of farms and for the identified goalInformation model practicalexamplefarm: an area organised by an operator to perform activities related to animal keepingTo improve the consensus of this definition I can refer to legislation, or scientific publicationsInformation model practicalexamplefarm: an areaorganised by an operator to perform activities related to animal keepingDictionary[.]

6 ]Area. surface specialised for animal keeping. Specifically, land parcels organised for animal confinement. This area can consist of permanent or semi-permanent structures such as buildings, shelters, or it can be delimited with fences, walls or boundary model practicalexamplefarm: an areaorganised by an operator to perform activities related to animal keepingDictionary[..]Area. surface specialised for animal keeping. Specifically, land parcels organised for animal confinement. This area can consist of permanent or semi-permanent structures such as buildings, shelters, or it can be delimited with fences, walls or boundary model practicalexampleStep 2:Spatial Characteristic[..] all areas dedicated to animal containment that are characterised by the presence of physical delimitation [.

7 ]physical delimitationcan be composed of man-made constructions such buildings, shelters, fences, walls, electric fences and natural barriers that functionally are used to contain the animalsInformation model practicalexampleStep 3:Primitiveand attributesTradeoff:Information model practicalexampleStep 3:Primitiveand attributesMethod:Primitive:Direct vs IndirectPolygon vs PointInformation model practicalexampleStep 3:Primitive and attributesData independence principle to assign a code to the farm (join function) to know when the spatial data was captured to know which capture method was used to know who captured the spatial data other geographical ancillary information ( : address)Information model practicalexampleStep 4:evaluate the data quality For a sample of not less than 10% of captured farm evaluate the spatial accuracy by means of a different data capturing method Calculate the error as the distance between the locations obtained by the two different methods for the same object.

8 The mean, the minimum and the maximum distances of the sampled farms provide us a sort of quality value for the collected dataInformation model practicalexampleQuestions?How best georeference a farm? 1) Geocoding2) Direct3) IndirectHow best georeference a farm? -GeocodingHow best georeference a farm? -GeocodingYouneed: Address locator software Background-address a collaborative project to create a free editable map of the world (Open Data Commons Open Database License). Google maps must be used according to the Google terms of serviceHow best georeference a farm? -GeocodingHow best georeference a farm? -GeocodingHow best georeference a farm? -DirectHow best georeference a farm? -DirectHow best georeference a farm? -DirectHow best georeference a farm?

9 -IndirectHow best georeference a farm? -IndirectHow best georeference a farm? -IndirectHow best georeference a farm? Questions?