Things you need to understand about metadata (NPC)

Things you need to understand about metadata (NPC)

INTRODUCTION

1.1 What is Metadata?

Metadata is data that provides information about other data, but not the content of the data. Metadata describes the data practically so that others can understand them. It also describes the data syntactically (in an orderly manner) so that others can use them. Metadata is used to facilitate the understanding, usage, and management of data, both by humans and computers.

Metadata facilitates decisions about how to use and manage the datasets. Metadata is an instruction manual for data because it describes the "who", "what", "when", "where", "why", and "how" about the data. It is the record that is relied on to find out how a particular dataset was created.

In an item's metadata (e.g.. EA map, road layer, building footprints, etc.), you can record whatever information is important for your organization to know about that item. This might include information about how accurate and recent the item is, restrictions associated with using and sharing the item, important processes in its life cycle such as generalizing features. and so on.

In Environmental Systems Research Institute (ESRI) ArcGIS software, a dataset's metadata can be viewed in the 'Description" tab, either in ArceCatalog or by opening the item "Description' window from other ArcGIS Desktop applications.

1.2 Metadata Anatomy

Metadata comprises of the following parts:

1.2.1 Identification

This provides a brief narrative of your data. In other words, it summarizes the purpose of your data in a succinct way. For example, identification assigns the following to the

metadata:

(a) Title - Name of the datasets.

(b) Description - The features that are in the datasets and what they represent.

 (c) Keywords - Categorizing your data with predefined taxonomy (classification).

1.2.2 Contact

The contact information includes details of who developed and makes the data available. It

includes the following three entities;

(a) Originator - who developed the data set.

(b) Publisher - who assisted in producing, editing and finalizing the end product.

(c) Distributor-who makes the data available.

1.2.3 Quality

Quality explains the accuracy and standards of the datasets. In spatial datasets, it includes the horizontal and vertical accuracy. Quality also evaluates tests of completeness and integrity of the data.

1.2.4 Spatial Reference

Spatial reference information explains geographic extent and coordinate system (projection) of a dataset. Projection information includes spheroid, datum and units. For example. Universal Transverse Mercator (UTM) and Minna Datum are common coordinate systems. Geographic extent comes in the form of a bounding box, place keyword or thumbnail.

1.2.5 Entities and Attributes

Entities refer to the map data types such as points, lines, polygons or grids. The purpose of this metadata item is to describe how the spatial information in the data is represented. For the entity attributes, it includes a description with a list of valid values and domains.

1.2.6 Lineage

Lineage describes in detail how the dataset was constructed. It lists the processing steps and responsible parties. Each processing step has a date when it took place so that users can track changes. It is like a change log listing the evolution of the data from start to finish.

1.2.7 Legal

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1.2.5 Entities and Attributes

Entities refer to the map data types such as points, lines, polygons or grids. The purpose of this metadata item is to describe how the spatial information in the data is represented. For the entity attributes, it includes a description with a list of valid values and domains.

1.2.6 Lineage

Lineage describes in detail how the dataset was constructed. It lists the processing steps and responsible parties. Each processing step has a date when it took place so that users can track changes. It is like a change log listing the evolution of the data from start to finish.

1.2.7 Legal

The legal section outlines the constraints for accessing and distributing the data. It describes the liability to assure protection of privacy and intellectual property. Metadata includes a security classification which handles the restriction over security concerns. For instance, confidential, restricted, sensitive, unrestricted and unclassified are examples of security classification in metadata.

1.2.8 Temporal

Temporal information focuses on when the data was collected or updated and how long it is valid. It also states progress such as when future updates are scheduled. The frequency of updates can be daily, weekly, monthly, annually, etc.

1.2.9 Metadata Reference

Metadata reference section is specific to the datasets referred to. It gives information on how to cite the datasets when used. The metadata reference has a temporal component for the date it was created and when it will be revised.

1.2.10 Metadata Standard

Several Committees from around the world have developed their own guidelines and standards for metadata. For GIS metadata standards, geographic data providers follow guidelines from the following organizations:

(a) Exduenl Canamahin Flats Cranmittaa (ECDC)

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(b) Registration Area (RA) Boundaries/Wards (FCT only), List of Localities with their

Polling Unit points and description of their RA/Wards were collected from the

Independent National Electoral Commission (INEC). National Population

Commission collected the boundaries on ground and digitized them.

2.3 Datasets Description:

598,988 Enumeration Areas (EAs) covering 774 Local Government Areas (LGAs) of the 36

States and the FCT.

Current File storage:

File Geodatabase (ArcGIS).

Access/Use Constraints: Selected Enumeration Areas available for public consumption based

on request/purpose.

2.4 Purpose:

A Sustainable National Geographic Frame for Censuses and Surveys.

2.5 Cross Reference/Larger work Citation

National Population Commission (2020): Delineation of Enumeration Areas Countrywide:

Training and Reference Manual for Enumeration Area Demarcation. National PopulationvCommission, Abuja.

National Population Commission (2016): Geographic Information System (GIS) Manual for Enumeration Area (EA) Database Creation. National Population Commission, Abuja.

United Nations (2017): Principles and Recommendation for Population and Housing

Censuses (Revision 3). United Nations, New York.

2.6 Time Period

November 2014 - April 2022.

2.7 Data Sources

Field visits by Party of Demarcators (the Honourable Federal Commissioners, State Directors, State Coordinators, Heads of Technical (HOT), GIS Data Entry Officers, Quality Assurance Personnel, Information and Communication Technology (ICT) Officers, LGA Comptrollers, Monitoring and Evaluation (M&E) Officers, Supervisors, Demarcators and Local Guides.

Existing Sources; Registration Areas (RA)/Ward boundaries from INEC, LGA boundaries from OSGOF, Compendium of Localities from National Population Commission, and

Satellite Imagery some of which were from OSGOF and others acquired by the Commission.

2.11 Methodology 

(DataCapturing.

Data Processing.

Data storage

and GIS Methodology Presentation). used

Methodology key words; Mobile GIS, EADPad

2.12 Analytical Models

NPCEADGIS TOOLS (building verification, dissolving and coding).

Field calculator (spelling checks and uniformity of codes).

2.13 Attribute Accuracy Report

Quality Assurance Methodology.

Sample Field Visits.

2.14

Completeness Report

Datasets acquired in 18 Phases Spanning November 2014 - April 2022 (see Appendix 5).

2.15

Spatial reference

Geographic Coordinates System (WGS 84)

Angular Unit: Degree (0.0174532925199433)

Prime Meridian: Greenwich (0.0)

Datum: D WGS 1984

Spheroid: WGS_1984

Semi-major Axis: 6378137.0

Semi-minor Axis: 6356752.314245179

Inverse Flattening: 298.257223563.

2.16 Process Steps

Step 1-Creation of GDB

Catalog Tools - GDB

Step 2 - Data Model

Point: BUILDINGS, IMPORTANT FEATURES

Lines: ROADS, DRAINAGE, RAILWAY

Polygons:

WATERBODY.

ENUMERATION AREA.

LOCALITY, RA_WARDS, LGA, STATE.

SUPERVISORY_AREA,

Field Generation and Naming (See Chapter 3: Entity Frame Data Dictionaries

Tools used

a. Phases: Pilot, 1 & 2

i Data Collection - PAPI - (Paper and Pencil Interview)

ii. Data Entry-On-field GIS data entry

b. Phases 3-7

Data Collection - Semi- CAPI using CSPro and Paper based Maps

Data Entry-On Field GIS data entry

c. Phases 8-9A & B

Data Collection - Transition to CAPI (Paperless with EADPad)

ii. Data Entry: On-field GIS Data entry

d. Phases 10-17

i.

Data Collection - CAPI (Paperless using improved EADPad 5.0)

ii. Data Entry: On-field GIS data entry using Geo-Processing tools for Coding.

Querying and Geographic and Administrative dissolve tools.

e. Phase 18: Pilot - Phase 9 LGAs datasets were updated

i Data Collection - CAPI (Paperless using EADPad Version 18 Update)

Data Entry: On-field GIS data entry using Geo-Processing tools for Coding.

Querying and Geographic and Administrative dissolve tools,

Step 5 - Data Input

Data collection from Field (Demarcators)

Description:

Attribute Data Collection and carving of EAs

Data Entry (Data Entry Officers)

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Date of Data Collection

Processing and Display of Demarcated EAS

Month Year of each Phase

2.17 Distribution Info

Request for any of the datasets should be addressed to the Chairman, National Population

Commission. Provision will be based on the extant rules guiding the distribution. Use of any

of our datasets is restricted to the requested purpose and should not be shared with a third

party.

2.18 Advice to Users of Data Sets

Users should assess "fit for purpose" use of datasets. The datasets were produced for

Censuses and Surveys.

Geodatabase. Each of them has a geometry type of point, line or polygon accordingly, Geo-

database type used is File Geodata, which has all files in a folder that can store, query

and manage

spatial and attribute

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Goodatabase is preferred over Personal and

Enterprise Geodatabases because of its ease of use and adequate storage facility for the EAD.

3.3 EAD FILE GEODATABASE STRUCTURE

EAD File Geodatabase has three primary components:

(a) Feature Datasets

(b) Feature Classes, and

(c) Non-spatial Tables

All three components are created and managed in Arc Catalog

The Components of the EAD File Geodatabase are explained as follows:

(1) Feature Datasets: This is the folder that stores all the feature classes (EAD entities).

All the feature classes have the same spatial reference. The Feature Datasets is named

ENUMERATION.

(n) Feature class: Each feature class is the representation of a typical EAD feature with a

general geometry (point, line, or polygon) and a common spatial reference. The NPC EAD Feature classes are as shown in Figure 3.1.

(iii)Non-spatial Table: This contains attribute data associated with each of the feature

classes

Table 3.1: EAD Feature Classes

SN

FEATURE NAME

GEOMETRY TYPE SOURCE

1.BUILDING POINT

NPC EAD FIELDWORK NPC EAD FIELDWORK

2 3.IMPORTANT FEATURE POINT ROAD POLYLINE

NPC EXTRACTION FROM SATELLITE IMAGERY NPC EXTRACTION FROM SATELLITE IMAGERY NPC EXTRACTION FROM SATELLITE IMAGERY NPC EA DISSOLVE

4.

DRAINAGE

POLYLINE

5.

RAILWAY

POLYLINE

6.ENUMERATION AREA SUPERVISORY AREA

POLYGON POLYGON

NPC EAD FIELDWORK NPC EA AGGREGATION

8.LOCALITY POLYGON

9.UNDEMARCATED AREA POLYGON

NPC EAD FIELDWORK NPC EA DISSOLVE

10.REGISTRATION AREA POLYGON

WARD LGA

11.POLYGON STATE WATERBODY

NPC EA DISSOLVED

POLYGON

NPC EXTRACTION FROM SATELLITE IMAGERY

CONCEPTUAL DEFINITION OF THE FEATURE CLASSES

1. Building: A building is any free-standing structure comprising of one or more rooms, covered by a roof or not, and may or may not be enclosed within external or dividing walls. A building may be used for Residential, Commercial, or Industrial purposes. It can therefore be a Factory, Shop, dwelling apartment, garage etc. A building may be used for multiple purposes.

NATIONAL POPULATION COMMISSION (NPC) ENUMERATION AREA DEMARCATION (EAD) GEOGRAPHIC INFORMATION SYSTEM (GIS)

STRUCTURE

NPC shifted from using the analogue method that was adopted at the early stage of the EAD exercise to digital method for delineating the entire country into smaller working units (best global practices). This is due to advances in mapping technology. This was done using Geographic Information System (GIS) Methodology.

The Geographic Information System (GIS) involves the following stages;

(a) Data Acquisition: Capturing of spatial and attribute data of entities.

(b) Data Processing: Storage, query, cleaning, manipulation and analysis of data. (c) Data Display and Output: The production and presentation of National, State and

LGA Spatial Frame in a Geodatabase for Censuses and Surveys,

These processes were customized for use in the form of Computer Aided Personal

Interviewing (CAPI) and Pen-and-Paper Personal Interviews (PAPI) as applicable.

3.1 DATABASE

A database is an organized collection of structured information or data, typically stored electronically in a computer system. A Geodatabase (GDB) is a database designed to store, query, manipulate and analyze Geographic Information and Spatial Data:

3.2 NPC GEODATABASE

NPC Geodatabase comprises of

(a) EAD Vector data acquired in associated reference system (Geographic Coordinate

System), structured and stored in the Geodatabase, and

(b) Satellite Imagery used for the Enumeration Area Demarcation (EAD),

The Vector data are representative of real-world features (the Census entities) in the EAD Geodatabase. Each of them has a geometry type of point, line or polygon accordingly. Geo- database type used is File Geodatabase, which has all files in a folder that can store, query and manage spatial and attribute data. The file Geodatabase is preferred over Personal and Enterprise Geodatabases because of its ease of use and adequate storage facility for the EAD.

3.3 EAD FILE GEODATABASE STRUCTURE

EAD File Geodatabase has three primary components: you can download the PDF here 

https://drive.google.com/file/d/1b3ukyB4XnotRUXEgEqzErmcUQcUMp1_Y/view

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