PTTPTT--102003102003SISTEM INFORMASI SISTEM INFORMASI

SUMBERDAYA LAHANSUMBERDAYA LAHAN

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INPUT DATA GEOGRAFIK

PENDAHULUAN

Input data geografik merupakan pekerjaan yang membutuhkan tenaga, waktu dan biaya yang cukup banyak (85 %) Minggu ini kita mempelajari sumber data

dan cara input data. Sumber: primer dan sekender Cara: capture dan transfer

Data Input How do I transfer the paper map data and

attribute data to a format that is usable by the GISsoftware?

Data input involves both locational (map) andattribute data.

The data can originate from various sources:– paper maps– attribute data on paper– other digital formats- databases (dBase), spreadsheets

(excel), or ASCII files

Sumber data

Source Raster VektorPrimary Digital Satellite RS

ImageGPS

MeasurementDigital aerial

photographsSurvey

MeasurementSecondary Scanned maps or

photographsTopographic maps

Digital elevation models from topographic map contour

Toponymy (placename) database

Alur Input data

Planning

Digitizing/ Transfer

Editing/ Improvement

Evaluation Preparation

DATA PRIMER

Data Raster: dari citra penginderaan jauh: AVHRR, Landsat, Aster, Spot, Ikonos, Quickbird, dll.– Dipilih sesuai dengan tujuan

Data Vektor: GPS– Ground survey membutuhkan waktu yang

cukup banyak.

DATA SEKUNDER

Data Raster: Media analog cetakan di scan dengan resolusi sesuai kebutuhan (100 dpi, 200 dpi, 400 dpi, dst).– Untuk perencanaan detil perlu discan dengan

dpi tinggi. Data Vektor:

– Digitasi manual: menggunakan meja digitasi– Heads-up digitizing and vectorization– Kesalahan digitasi– Fotogrametri.

Keyboard entry:(the source data only exists on paper)

mainly attribute data type data using keyboard data can be entered directly

into a GIS table, spreadsheet, or database table.

Land survey:

calculates coordinates on location (in the field) by measuring distances and angles, then entering the values into the software

process uses coordinate geometry (COGO)

process is used to draw legal documents ie. Parcel properties

Digitizing: A process that uses a device

to extract spatial features from paper maps or photos to electronic GIS format

Digitizing hardware:– table or tablet– grid of wires embedded in

surface• grid generates a magnetic

field • that can be detected by a

cursor– cursor is a small flat device

that contains a wire cross hair

• cursor keypad allows special

Modes of Digitizing

Two modes of digitizing:• point user identifies points to capture individually by

pressing enter on cursor• stream points captured at set time intervals and/or

movement of cursor

Point Stream

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Manual Digitizing ?

The majority of spatial data entered into a GIS is from manual digitizing.

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Manual Digitizing

The digitizing tablet and table allow information to be traced from an existing map or graphic. Three different types of tables or tablets

exist.– (1) Acoustic – the digitizing pen emits a high

frequency sound that is received by microphones at the corners of the work area, triangulation is used to calculate the x and y coordinate of the pen.

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GTCO CalComp Sonic Digitizer

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Types of Digitizers (Continued) (2) Resistivity uses two charged pads

separated by a thin air gap, x and y coordinates are determined when the pads make contact. (3) The most widely used in large scale

digitizers is the electronic digitizing tablet. Embedded below the surface of the table or the tablet is a grid of wires that measure the strength of the signal from the puck or the pen

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Qualities of a Digitizer

– Stability • The ability of the digitizer to maintain a

value as the puck remains in one place.– Repeatability

• Precision• Good digitizers accurate to 0.001 inch

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Qualities of a Digitizer #2

– Linearity • the ability to be within a specified distance of

the correct value• Good digitizers are able to have a linearity of

0.003 inch over 60 inches– Skew

• The ability to produce coordinates in a true rectangle.

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Digitizing Procedures The Map is fixed to the digitizing table. Three or more control points are digitized.

– Easily identified points (intersections of major streets, major peaks, points on coastline)

– These coordinates will be known or verified– The digitizing area is registered to the map area.

Digitizing the map can be done in two ways.– In point mode , the operator identifies the points

captured explicitly by pressing a button.– In stream mode the points are captured at regular

intervals (time or distance)

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Digitizing Procedures (cont)

Point mode is done subjectively by the operator (no two operators will digitize the same). Stream mode generates a large number of

points, many of which will be redundant. Most digitizing is done in point mode.

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Advantages of Digitizing

Low initial capital cost Flexible and adapts to different types of

data Easily mastered skill Digitizing devices are reliable Generally the quality of data is high

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Digitizing Vendors

Altek Calcomp Didger GTCO Kurta

ProblemsProblems or Errors using Digitizing:- Paper maps can stretch/ shrink. Lose accuracy.- Paper maps meant to display information, not

record locational (x,y) information.- Discrepancies across map sheets to digitize. (ie

roads do not match when 2 maps digitized.)- User error such as overshoots, undershoots, or

spikes

Overshoot Undershoot Spike

To avoid or correct overshoots, undershoots, or spikes:• use clean function•“snap” to nodes

Before After

Problems

overshoot

undershoot

Dangling segmen

Sliver polygon

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Scanning Technology

Converts paper maps into digital format by capturing features as cells, or pixels. Cells are captured using a scanner head

made up of photosensitive cells. Advanced large format scanners have

heads with 8000 photosensitive cells Each sensor is able to record a pixel rated

between 0 (black) to 255 (white) and any graytones between.

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Color Scanning Technology

Color images use the same technique but the image is scanned for red, blue and green. Older scanners required the image being

scanned to pass the scanning head in three passes. Vectorization often requires color scanning

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Color Scanning Technology

Filters allow the head to pass the image once scanning all three colors at once The latest technology: full width, single

line, sensor array scanning uses a line of LED’s which capture the image LED scanners can create images using 16.8

million colors at speeds several times faster than previously obtained.

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Scanning Problems Higher resolutions aren’t always the answer to

better data; often the additional “noise” and resulting clean up of data can cause higher resolution to not be the best solution, a balance between detail and additional manual clean-up must be struck.

Paper maps are not “dimensionally stable” and a great deal of variation occurs as the maps age.

Documents must be clean (no smudges or extra marks or lines).

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Scanning Problems #2

Text may accidentally be scanned as line features in automatic feature recognition. Specialized symbols (for example marsh or

asphalt) may not be detected as such.

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IDEALLarge Format Monochrome Scanners

Model Pricemax dpi

Paper Size Speed

FSS 4300DSP $6,675 200 36 in. 15 sec.

FSS 8300DSP $10,425 800 36 in.17 sec.@200 dpi

FSS 12300DSP $11,925 1200 36 in.25 sec.@200 dpi

FSS 18300DSP $13,425 1800 36 in.34 sec.@200 dpi

Super Wide 2250 $13,425 400 50 in. 3 in./sec.

Super Wide 2251 $14,925 800 50 in. 6 in./sec

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ANAtechBinary & Grayscale Scanners

Evolution 4 $10,000 400 36 in.3"/sec @ 200 dpi

Evolution 8 $11,000 800 36 in.3"/sec @ 200 dpi

Evolution Pro $12,500 800 36 in.6.4"/sec @ 200 dpi

High Resolution Monochrome Scanners1270 Digidot $50,000 1270 27 in. UnknownEagle 4225 $55,000 2540 42 in. Unknown

Model Price max dpiPaper Size Speed

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Large Format Color ScannersESC 5010 DSP $11,175 500 36 in.

36 sec.@200 dpi

FSC 8010 DSP $14,925 800 36 in.

48 sec.@200 dpi

Large Format Color ScannersColortrac 5480 $31,000 800 54 in.

1.5"/sec. @ 200dpi

Eagle 6250C $142,000 1000 62 in. Unknown

ModelPrice

max dpiPaper Size Speed

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Vendors for Scanners

Widecom Scanners– www.widecom.com/

Anatech Scanners– www.anatech.com/

Vidar Systems Corporation– www.delinfotek.com/

Abakos Digital Images– www.abakos.com.au/

Contex Scanning Technologies– www.caddcentreindia.com/

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Digitizer or Scanner Scanners

– Speed and ease– Raster data without

intelligence; manual or automatic vectorisation possible.

– Usually produces large files that need compression

– Hardware is expensive

Digitizers– Labor intensive– Requires skilled operator– Vector (intelligent) data– Labor intensive– Hardware less expensive

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Scanning & Digitizing Input Errors

Incompleteness of the spatial data; missing points, line segments, and polygons. Location placement errors of spatial data;

careless digitizing or poor quality of the original source. Distortion of spatial data; base maps that

aren’t scale correct over the entire image or from material stretch in paper maps.

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Scanning & Digitizing Input Errors #2

Incorrect linkage between spatial and attribute data; misplaced labels or unique identifiers being assigned during manual key entry or during the initial setup.

Attribute data is wrong or incomplete; missing data records or data records from different time periods.

Redundant information, including vertices, text, nodes, and arcs.

Incorrect label information and placement.

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Common Spatial Errors

Slivers or gaps in the line work. Dead ends, dangling arcs, overshoots and

undershoots. Bow ties or weird polygons caused by

inappropriate closings of connecting features.

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Data Verification

Visual review; usually done by reviewing a check plot (hard copy).

Cleanup of lines and junctions; this process is usually done by software and then through manual editing.

Check source maps, if additional copies of the same map are available compare them to see if stretching of the map has occurred.

Check output drawing to see if text or symbols were read as features if software is used to convert the drawings.

DATA TRANSFER

Dari format data lain

Data Yang DimasukkanDATA ANALOG

– Peta – Data Tabulasi

DATA DIGITAL– Peta– Tabel

• Disesuaikan dengan tujuan dan data yang tersedia

• Menentukan keefisienan dan keefektifan sistem pengelolaan data dalam SIG

• Berpengaruh terhadap besarnya data yang diperlukan

PERSIAPAN PEMASUKAN DATATERGANTUNG DARI DATA YANG TERSEDIA

Data tabular: diketik ke dalam “spread sheet” Foto Udara:

– Interpretasi– Koreksi geografik– Digitasi

Data dijital lain– Konversi ke format yang dituju

Data lapangan:– Tabulasi– Klasifikasi

PERSIAPAN PEMASUKAN DATA

a. Kualitas data sering dipengaruhi oleh lembaga penghasil dataLokal:

– hanya untuk kepentingan sendiri sulit diintegrasi

Regional/Nasional: – untuk kepentingan banyak pemakai mudah diintegrasi

b. Sumber data• lapangan

• interpretasi citra (foto udara/satelit)

Pertimbangan lain:

PERSIAPAN PEMASUKAN DATA

c. Waktu pengambilan

tergantung macam data:

data vegetasi/penggunaan lahan sebaiknya yang terbaru

tanah: bisa lama asal klasifikasinya sama

untuk monitoring: periode waktu tertentu tergantung tujuan, harian, mingguan, bulanan, tahunan, dll

Pertimbangan lain:

d. Lain-lain

SUMBER & ALAT PEMASUKAN DATA SPASIAL

SUMBER DATA ALAT PEMASUKAN

Peta Analog, Foto Udara, dll

Meja digitasiScanner digitasi di layar

Data tabel Keyboard

Data dijital Konversi ke format yang dituju Floppy disk CD Dll

Koordinat Lapangan

GPS

Dll …. Dll …..

Editing

1. Berkaitan dengan kondisi geometrika. Node hilang/bergeserb. Ujung hilang/bergeser

2. Berkaitan dengan topologi:a. Ujung tidak berkaitanb. Ada antara/gapc. Garis gandad. Garis lebihe. Poligon anehf. dll

Dilakukan bila ada kesalahan dalam pendigitasian dengan menggunakan meja digitasi

Pemasukan dengan Scanner

Produknya berupa data raster Perlu perampingan bentuk garis agar

koordinatnya dapat dikenali dengan baik Kadang perlu vektorisasi Untuk data yang kompleks (misal peta

topografi), seringkali harus dilakukan penggambaran kembali

Ada dua macam: – flat-bed scanner – drum-scanner

Pemasukan dengan Digitasi Layar Komputer

Peta disiam (dengan menggunakan scanner)

Ditampilkan pada layar monitor Didigitasi langsung di layar (+ editing jika

terjadi kesalahan) Registrasi untuk mendapatkan koordinat Bermanfaat untuk menambah informasi

yang tidak terdapat pada peta asli, misal pola drainase yang wilayah berbukit/bergunung. Dengan melakukan overlay dengan foto udara atau citra satelit pola drainase dapat ditambahkan.

Pemasukan data dengan GPS

Untuk koreksi geometri Menentukan koordinat obyek di lapangan

secara tepat, misal lokasi pemboran, minipit, profil tanah dsb.

Bisa berfungsi sebagai digitasi obyek di lapangan

Kelemahan: membutuhkan ruang terbuka, pada ruang yang tertutup (dibawah pohon) menghasilkan deviasi yang besar

Digitasi konvensional vs GPSKONVENSIONAL GPS

Ketelitian bergantung skala Ketelitian tidak bergantung skala

Cocok untuk koleksi data yang besar Cocok untuk koleksi data yang selektif

Kecepatan pendigitasian dikontrol oleh pengguna

Kecepatan pendigitasian dikontrol oleh batas kecepatan dan kondisi lalu lintas

Cocok untuk obyek-2 yang dapat terlihat pada peta atau foto udara

Dapat juga digunakan untuk obyek-2 kecil

Digitizer 2 dimensi Digitizer 3 dimensi

Pendigitasian point-mode Pendigitasian dengan metode penentukan posisi statik singkat, stop and go atau pseudo-kinematik

Pendigitasian stream-mode Pendigitasian dengan metode penentukan posisi kinematik GPS

Operator lapangan harus terlatih Staff biasa dapat melakukan pengukuran

Perlu ada “land mark” lapang Perlu ada “land mark” lapang

Data non digital Data digital

PEMANFAAT DATA DIGITAL Dinegera maju data digital dan

pendukungnya sudah banyak tersedia Di Indonesia sedang dirintis Lembaga yang mengurusi:

BAKOSURTANAL (Badan Koordinasi Survei dan Pemetaan Nasional) Format data spasial yang ada: ArcInfo, ArcView, Erdas, Idrisi, ILWIS,

Auto-cad, MapInfo, kadang juga dalam bentuk BMP, TIFF, JPG.

DATA YANG TERSEDIA

Data kartografik:– Bakosurtanal

Data sumberdaya alam– Tanah: Puslitbangtanak, Bogor– Penggunaan Lahan: BPN– Geologi: Puslitbang Geologi Bandung

Data elevasi digital Data kartografik berkaitan dengan sensus

– BPS