1. Project Overview & Basic Rules

Summary

• Project introduction
• Overview of project tasks
• Workflow
• Working area
• Basic rules
• Building interpretation methods & typical cases
• Building interpretation methods
• Building categories
• Residential geography
• Condo / commercial / industrial geography
• Dense building block geography
• Farmland/rural geography

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Content : from 2D imagery, draw the 3D building structure using the rooftop as a starting point

Project introduction

• Overview of project tasks

labeller

checker

errors exist, pushed back

finish task, submit

Project introduction

• Workflow

errors exist, pushed back

passed, submit

Judger

Final approval

Online system

Labeler’s task: draw images following project requirements; then revise results based on checkers feedback.

Checker’s task: check labeler’s drawing result, and also add revision comments

The loop will be complete when the task is approved by the Checker.

1

2

4

3

Task area

No

Yes

No

No

No

Yes

Yes

Yes

No

Yes

Yes

Task area (“assistant grid”)

• Buildings entirely located in your own task area must be drawn;
• Buildings partially located (one pixel or more) in your task area and any other region besides 1,2,3,4, must also be drawn.
• Any buildings partially located in areas 1, 2, 3, or 4 are not to be drawn;

Project introduction

• Working area

• 1. Shape: The geometric shape of building rooftops is a polygon. Usually the opposite lines are parallel; adjacent lines are perpendicular (ie. residential houses & industrial buildings). Some buildings might have unique shapes, such as oval, diamond, or other irregular shapes (ie. shopping malls, office buildings, high rise apartments).

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• 2. Accuracy: Drawings of building rooftops must be accurate within 3 pixels. Small angles/corners within 3 pixels can be simplified (no matter drawn or not is acceptable). However, redundant angles/corners are not allowed.

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Drawing rules

• Buildings with consistent height (single layer structure): only draw one layer
• Buildings with multiple structures (multi-layer structures): draw one layer then cut follow the structure parts

Project introduction

Basic rules

• Basic rules
• 1. Shape: The geometric shape of building rooftops is a polygon. Usually the opposite lines are parallel; adjacent lines are perpendicular.

Project introduction

• Basic rules
• 2. Accuracy: Drawings of building rooftops must be accurate within 3 pixels. Small angles within 3 pixels can be simplified (no matter drawn or not is acceptable). However, drawing non-existing/redundant angles are not allowed.

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Sample 1: Small angles within 3 pixels can be passed (no matter drawn or not).

Project introduction

• Basic rules
• 2. Accuracy: Drawings of building rooftops must be accurate within 3 pixels. Small angles within 3 pixels can be simplified (no matter drawn or not is acceptable). However, redundant angles are not allowed.

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Sample 2: Small angles within 3 pixels can be passed (no matter drawn or not).

Project introduction

• Basic rules
• 2. Accuracy: Drawings of building rooftops must be accurate within 3 pixels. Small angles within 3 pixels can be simplified (no matter drawn or not is acceptable). However, redundant angles are not allowed.

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Sample 3: Redundant angles are not allowed

Project introduction

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Building interpretation methods & typical cases

• Building interpretation methods
• To understand and distinguish each object on the property based on context, shape, color, and texture.
• Building categories & samples
• Residential geography
1. single-family buildings
2. Townhouses
3. Dense buildings
• Condo / commercial / industrial geography
• low-rise
• high-rise
• Dense building block geography
• Farmland geography

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• To understand and distinguish each object on the property, use:
• Context: The relative location of each object on the property
• Shape: The geometric shape of each object.
• Color: The color of each object.
• Texture: The texture of each object (ie. smooth, rough)

1. Building interpretation overview

i. Overview - using visual features to distinguish objects on property

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Primary building: in centre of property

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Pool: in the back

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Private road: leads from public road to primary building

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Shadow: on side and between levels and adjoining buildings

Solar panel: on top of the roof of the primary building

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1. Building interpretation overview

ii. Context

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• Context: The relative location of each object on the property

Fences: line the boundaries of the property

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Attached buildings (such as shed and deck) : at the side of primary building

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Primary building: rigid and parallel lines, right- angle edges

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Pool: oval or square

Private road: long with parallel sides

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Shadow: follows shape of roof

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Fences: straight, long, thin

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1. Building interpretation overview

iii. Shape

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• Shape: The geometric shape of each object

Solar panel: rigid and parallel lines, right-angle edges

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Attached buildings (such as shed and deck) : right-angle polygon, same as primary building

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Primary building: brown, white, grey, black and so on

Pool: blue, dark blue, or light yellow (based on the water depth)

Private road: brown, grey, or black

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Shadow: black

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Fences: brown, white or black

1. Building interpretation overview

iv. Color

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• Color: The color of each object

Solar panel: black or grey, there are white lines on it

Attached buildings (such as shed and deck) : most are white and ivory, some are black, grey, or dark green

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Primary building: slightly rough, hunch-up feel made by roof arch

Pool: continuous, smooth

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Private road: slightly rough but more smooth than primary building

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Shadow: smooth

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Fences: continuous, smooth

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1. Building interpretation overview

v. Texture

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• Texture: The texture of each object

Solar panel: grid texture

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Attached buildings (such as shed and deck) :more smooth than primary building, no roof arch, flat, some times has stripes.

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Residential: Single-family buildings

1. Single-family buildings

i. Drawing rules - Draw primary building and other permanent structures

ii. Common errors

1. Attached building (shed and deck) missed or wrong

2. Small buildings missed (buildings lager than 36 pixels should be drawn)

3. Incorrect merging / separation

4. Road / walkway as building

5. Yard as building

6. Inner yards should be excluded

7. Trees cover causes part of the building missing

8. Shadow

9. Roof arch drawn

10. Incorrect multilayer structure

iii. Other drawing rules

• Building under construction
• Caravans
• Tent/sunshed
• Trampoline

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Residential: a. Single-family buildings

i. Drawing rules - Draw primary building and other permanent structures, merge if adjoining

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Use fences to guide property & building separation

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Do not be tricked by private road that is similar color as building

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Draw primary building on property

Draw & merge any adjoining buildings / parts, such as shed

Do not draw the pool

Do not be tricked by shadow cast by building

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Draw the shadow cast by building height difference

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• Shed and deck should be drawn together with primary building as one building. Interpretation based on these rules below,
• Context: Attached part (shed and deck) is located at the side and back of the primary building, adjoining with the primary building.
• Shape: normalized shape, righ-angle and paralleled lines, simillar with primary building
• Color：most are white, light grey, sometimes are dark colors
• Texture：flat, no roof arch, sometimes has stripes

Residential: a. Single-family buildings

ii. Common errors – 1.Attached building (shed and deck) missed or wrong

shed

deck

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• Shed and deck should be drawn together with primary building as one building

- Case 1

Context: located at the side or back and adjoining with primary building

Residential: a. Single-family buildings

ii. Common errors – 1.Attached building (shed and deck) missed or wrong

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Incorrect

Shape: similar with primary building

Color: ivory, light grey

Texture: flat, no roof arch

Correct

Attached building missed

Primary and attached building drawn as one building

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• Shed and deck should be drawn together with primary building as one building - Case 2
• ​

Residential: a. Single-family buildings

ii. Common errors – 1.Attached building (shed and deck) missed or wrong

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Draw shed and primary building as one building

Incorrect

Correct

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• Small buildings larger than 36 pixels need drawn (this rule may change based on different projects). Interpretation based on these rules below,
• Context: located at the back, near to fences
• Shape: most are rectangle
• Color: most are white, grey, brown, some are black or in black and white stripes.
• Texture: similar with primary building, some has roof arch

Residential: a. Single-family buildings

ii. Common errors – 2.Small building missed

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Blank image

Correct

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• Small buildings larger than 36 pixels need drawn – Case1

Context: located at the back, near to fences

Shape: rectangle

Color: grey, black

Incorrect

Correct

Texture: has roof arch, hunch-up

Residential: a. Single-family buildings

ii. Common errors – 2.Small building missed

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• Small buildings larger than 36 pixels need drawn – Case2

Incorrect

Street view

Context: located at the back, near to fences

Shape: rectangle

Color: grey, white, black

Texture: has roof arch, hunch-up

Residential: a. Single-family buildings

ii. Common errors – 2.Small building missed

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Incorrect drawing, parcel on

Incorrect drawing, parcel off

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• Draw buildings on each property separately. Interpretation based on the rules below,
• Context:

a. Properties will be separated by fence-lines, and have a separated yard

b. Each separate property will have its own private road

• Color: The color of separate buildings will usually be different
• Parcels：means the boundaries of each property. Parcels can be used as additional guides to verify separation suggested by visual features.

Context: (b) Two separate driveways

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Context: (b) Backyard separation

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Residential: a. Single-family buildings

ii. Common errors – 3. Incorrect merging / separation

Color: Roof color different

Parcel confirms need for separation

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• Case1

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Residential: a. Single-family buildings

ii. Common errors – 3. Incorrect merging / separation

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• Parcels：means the boundaries of each property. Parcels can be used to verify separation suggested by visual features.
• Case2

Based on parcels, the adjoining buildings belong to two properties, need separation

Separate based on visual features and parcels

Blank image

Correct

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Residential: a. Single-family buildings

ii. Common errors – 3. Incorrect merging / separation

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• Buildings not adjoining should draw separately and leave the space (based on the true situation)
• Case 3

Incorrect separation

Incorrect

Correct

Leave the space

Black image

Space between buildings

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• Do not draw private road / walkway as building
• Context: (a) buildings do not come that close to the road. (b) the distance from building to road is usually fairly consistent. (c) cars can park on the private road.
• Color: most are grey and black, while roof color changes more
• Texture: smooth, no arched feel

Residential: a. Single-family buildings

ii. Common errors – 4. Road / walkway as building

Context (c): cars parking

Color: grey

Texture: smooth, no arched feel

Context (b): the distance from building to road is fairly consistent

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Incorrect

Street view

Private road drawn as building

Residential: a. Single-family buildings

ii. Common errors – 4. Road / walkway as building

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Do not draw private road / walkway as building

• Case1

Context (a) buildings do not come that close to the road

Texture: smooth

Correct

Context (b): the distance from building to road is fairly consistent

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Incorrect

Blank image

Residential: a. Single-family buildings

ii. Common errors – 4. Road / walkway as building

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Do not draw private road / walkway as building

• Case2

Texture: smooth

Context (a) buildings do not come that close to the road

Private road drawn as building

Context (b): the distance from building to road is fairly consistent

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Context (a) fence shows the yard boundary, building can not be built fill in the fence

Context (b) building shadow shows the building shape

Residential: a. Single-family buildings

ii. Common errors – 5. Yard as building

• Do not draw surrounding area as building
• Context: (a) fence shows the yard boundary, building can not be built fill in the fence (b) building shadow shows the building shape, (c) building sizes in one block are nearly the same
• Color: most are different from roof color, yard will be bare-land (brown, dard red) or grass (green), not uniform
• Texture: yard is more rough, no arched feel, sometimes has objects on it (such as cars and trees)

Color: green

Texture: rough, has objects on it

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• Do not draw surrounding area as building
• Case1

Incorrect

Residential: a. Single-family buildings

ii. Common errors – 5. Yard as building

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Color:

inconsistent brown, bare-land

Yard as building

Street view

Texture: no arched feel

Context (a) fence shows the yard boundary, building can not be built fill in the fence

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Blank image

Incorrect

Correct

Residential: a. Single-family buildings

ii. Common errors – 5. Yard as building

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• Do not draw surrounding area as building
• Case2

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Context (c) building sizes in one block are nearly the same

Street view

Context (a) fence shows the yard boundary, building can not be built fill in the fence

Context (b) building shadow shows the building shape

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• Visable inner yards on the roof top should be erased
• - Case1

Correct

Incorrect

Inner yards show the ground, do not draw

Inner yards should be excluded

Residential: a. Single-family buildings

ii. Common errors – 6. Inner yards should be excluded

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Incorrect

Blank image

Shape: strange shape and strange corners

• Trees cover causes part of the building missing. Should draw based on the common sense. Interpretation based on the rules below,
• Context:trees cover appears arround the building and above the roof
• Shape: buildings do not have strange shape and strange corners

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Residential: a. Single-family buildings

ii. Common errors – 7. Trees cover

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Context:trees cover appears arround the building and above the roof

Correct

Draw based on the common sense

-Case1

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Incorrect

Blank image

• Trees cover causes part of the building missing. Should draw based on the common sense.
• - Case 2

Residential: a. Single-family buildings

ii. Common errors – 7. Trees cover

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Correct

Shape: strange shape and strange corners

Context:trees cover appears arround the building and above the roof

Draw based on the common sense

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Blank image

Incorrect

Correct

• Tricked by shadows causes wrong separation and shape. Interpretation based on the rules below,
• Context: no narrow alley or inlet in the center of the building
• Shape: buildings will not have unrealistic shapes and strange corners
• Color: roof color is consistent, the black narrow gap is caused by roof shadow, need to draw
• Case1

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Residential: a. Single-family buildings

ii. Common errors – 8. Shadow

Unrealistic narrow gap

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Blank image

Incorrect

Correct

Context：unrealistic alley or inlet

Shape：reasonable shape without strange corners

Residential: a. Single-family buildings

ii. Common errors – 8. Shadow

• Case2

Color: black narrow gap caused by roof shadow

Street view

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Blank image

Incorrect

Correct

Chimney

Shape: realistic building shape

Residential: a. Single-family buildings

ii. Common errors – 8. Shadow

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• Shadow caused by chimney
• - Case3
• Context: located at the roof edge, higher than roof, small shadow
• Shape: small square
• Texture: slightly heave

Unreasonable corners

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incorrect

correct

Be careful about the difference between height shadows and wall shadows

Residential: a. Single-family buildings

ii. Common errors – 8. Shadow

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• Shadows inside the building need draw – Case4

Color: black narrow gap caused by height shadow

interpretated as two buildings and separate

draw as one building

Blank image

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Correct

Incorrect

Wrong: Shadow draw as part of the building

• Do not draw shadows caused by wall. Interpretation based on rules below,
• Context: shadows are located at the same direction in one imagery (example, all the shadows are located on the left side of the objects)
• Color: black, darker than roof color
• Case 5

Residential: a. Single-family buildings

ii. Common errors – 8. Shadow

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Incorrect

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Black image

• Do not draw shadows on the sides of building.
• Case6

Residential: a. Single-family buildings

ii. Common errors – 8. Shadow

Context: shadows have same direction

Color: black

Correct

Wrong: Shadow draw as part of the building

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Incorrect

Roof arch shape is not the real building shape

• Do not draw the roof arch, draw a straight line
• Context：Visable roof arch cased by the image shoot angle
• Shape: Roof arch shape is not the real building shape. Building boundaries are straight lines.

Residential: a. Single-family buildings

ii. Common errors – 9. Roof arch drawn

Correct

Building boundaries are straight lines

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Incorrect

Context: visible roof arch

• Do not draw the roof arch, draw a straight line
• Case2

Residential: a. Single-family buildings

ii. Common errors – 9. Roof arch drawn

Correct

building boundaries are straight lines

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• Buildings under construction need to draw
• Context : located at bare-land
• Shape: same as common buildings, has right angles and parellel lines
• Color: lighter than common buildings, most are sand color
• Texture: rough

correct

blank image

Residential: a. Single-family buildings

iii. Other drawing rules – 1. Building under construction

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• Do not draw caravans
• Context：parking in the yard, bare-land and road
• Shape：small narrow rectangles
• Color：white
• Texture：Top of the caravans has vents and windows, front of the caravans has hooks

Residential: a. Single-family buildings

iii. Other drawing rules – 2. Caravan

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• Do not draw tent and sunshed
• Context: (a) in the back yard. (b) on the grass of the park (c) collective and uniform
• Color：white, ivory, blue
• Shape：circle, square, diamond and so on
• Texture：flat and smooth

Do not draw

Residential: a. Single-family buildings

iii. Other drawing rules – 3. Tent/sunshed

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• Do not draw trampoline
• Context: appear most commonly in the back yard of single-family residential buildings
• Shape: small circle
• Color: Dark, has light color edge
• Texture: not smooth

Residential: a. Single-family buildings

iii. Other drawing rules – 4. Trampoline

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b. Townhouses

i. Drawing rules - Draw townhouses as one first, then cut reasonably if you see obvious buildings edges.

Residential: b. Townhouses

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Residential: b. Townhouses

i. Drawing rules – Draw townhouses as one, then cut reasonably if you see obvious buildings edges

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Primary buildings draw as one building

• Townhouses need to be cut reasonably if you see obvious buildings edges.
• Context: (a) has similar height and built adjoining with each other (b) often have separate additional buildings in front or back
• Shape：(a) townhouses consist of the same building shape wil be repeated many times (b) roof top seems like one structure
• Color：usually be one consistent color
• Texture：roof has consistent texture

Adjoining attached structure should merge as one building

If attached structure is separate, then draw separately

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Residential: b. Townhouses

i. Drawing rules – Draw townhouses as one building, only merge adjoining additional buildings

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• Townhouses need to be cut reasonably if you see obvious buildings edges.
• Case1

Context (a) similar height and built adjoining

Shape (a)repeated building shape

Color:

consistent

Texture：consistent

Cut reasonably based on obvious buildings edges

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• Townhouses need to be cut reasonably if you see obvious buildings edges.

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Case2.

Residential: b. Townhouses

i. Common errors – not cut reasonably

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Incorrect

Correct

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Draw multi-layer structures --- obvious layers should be included.

Case 1： There are some significant building structures. You can check them by shadows caused by different heights.

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Draw obvious layers.

Cut them based on lines

Blank image

Correct

Condo/Commercial/Industrial: a. Low-rise

i. Drawing rules – Draw multi-layer structures

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• Inner yard should be excluded
• Context：inner yard is located inside of the building, no roof top, shows the ground
• Shape：different kinds of shape, most are rectangles

correct

blank image

incorrect

visable trees on the inner yard, do not draw

exclude the inner yard

Condo/Commercial: a. Low-rise

ii. Common errors – Inner yard are not excluded

This rooftop layer should be included. Use “father & son” method.

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• Undercover walkways joining multiple buildings would be represented as a single building
• Context：some buildings are linked by undercover walkways
• Shape：long and thin
• Color：similar as building rooftop
• Texture：similar as building rooftop

Correct

Blank image

Draw undercover walkways

Condo/Commercial/industrial：a. Low-rise

iii. Other drawing rules – 1. Undercover walkways would be drawn

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• pedestrian bridges larger than 3m (6 to 10 pixels) in width would be represented
• Context：above the road
• Shape：long
• Color：light colors, usually pure white, ivory white, grey
• Texture：similar as building rooftop

Pedestrian bridges above the road would be drawn

Condo/Commercial/industrial：a. Low-rise

iii. Other drawing rules – 2. pedestrian bridges larger than 3m in width would be drawn

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• Don’t draw artificial objects（tubes & pipes, materials for construction, wagon box, big container）
• Context：（1）usually appear on bare land in industrial area （2）concentrated
• Color：colors vary, usually light colors
• Shape：long & thin

Tubes & pipes

Wagon box

Big container

Materials for construction

Condo/Commercial/industrial：a. Low-rise

iii. Other drawing rules – 3.don’t draw artificial objects

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Dense Building Block

i. Drawing rules – draw as one, then cut where appropriate and reasonable. Remember to exclude any ground or yard. Draw multi-layers for those layers with significant height. Use “brother” method. (Refer to video tutorial for more details.)

ii. Common errors

• Incorrect merging/cutting
• Gaps between buildings adjoining with each other
• Forget to drag side-wall
• Missing multi-layers

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Dense Building Block

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• Draw as one, then separate where appropriate.
• context：（1）Has similar height and built adjoining with each other（2） the block is large（3）collectively appear
• shape：similar fashion & size
• color：color might vary
• texture：（1）dense but similar rooftop（2）inward areas might be backyard and ground

Dense Building Block

i. Drawing rules - draw as one, then cut where appropriate

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• Correct separation based on rules below：

（1）avoid ‘dead lock’ buildings – buildings have no link to road.

（2）separate appropriately based on different roof colors

（3）separate appropriately based on different roof textures, do not over-separate

（4）separate appropriately based on buildings edges.

Case 1 – “dead lock” buildings

dead lock

Correct

Incorrect

all the buildings should have path to enter

Dense Building Block

i. Drawing rules - draw as one, then cut where appropriate

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Cutting rules:

• Cut reasonably based on visible building boundaries
• Cut reasonably based on different roof colors (with sharp color transition)
• Cut reasonably based on different roof textures
• Don’t do over-cutting

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Case 1: Cut too roughly. Need more separation based on the cutting rules.

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Need to cut more

incorrect

Blank image

Dense Building Block

ii. Common errors – 1. Incorrect merging/cutting

correct

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• Don’t have gaps for buildings adjoining with each other. Don’t draw buildings one by one.
• Using “draw a block as a whole, then cut” technique can avoid this error.

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Case 1

Using “draw a block as a whole, then cut” technique can avoid this error.

Correct

Incorrect

Blank image

Dense Building Block

ii. Common errors – 2. gaps between buildings adjoining with each other

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i. Drawing rules:

1. Draw green houses
2. Draw silos (diameter ≥11 pixels)
• Tips for drawing round shape
3. Do not draw bushels of hay入

Farmland/rural area

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Blank image

Correct

Farmland/rural area

i. Drawing rules – 1. Draw greenhouses

• Draw greenhouses - Greenhouses are structures that are used to grow plants and crops
• Context: greenhouses appear in fields
• Color：white, grey
• Texture: greenhouses have a rough texture
• Shape: greenhouses appear as squares or rectangles

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• Draw silos (diameter ≥11 pixels)
• Context: silos will can appear in residential, commercial, or farmland geographies
• Shape: silos have a round shape
• Color：usually white, grey, sometimes dark color
• Don’t draw round objects look like ground

Draw

≥11个pixels

Draw

Don’t draw

Farmland/rural area

i. Drawing rules – 2. Draw silos

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• Tips for drawing round shape：
• Use arc tool
• （1）draw 2 points on the edge of silo. These 2 points must be very close to each other.（2）drag the arc，press “space” button to finish. The circle can be drawn accurately.

​

Incorrect

（1）draw 2 points close to each other

（2）drag the arc

Correct

Farmland/rural area

i. Drawing rules – 2. Draw silos

Summary

• Usually buildings have right angle corners, please use right angle tool(R)/right angle repair tool(X) to draw reasonable shape. Drawings of building rooftops must be accurate within 3 pixels
• Don’t draw road/walkway, backyard, tent, pool, container, caravan, bushels or any other non-building stuff.
• Don’t miss shed, small buildings, or other additional structures.
• Pay more attention to shadows. Don’t draw abnormal corners or do incorrect separation.
• Townhouses would be cut reasonably based on rooftop edges.
• Separate dense buildings properly. Don’t draw “deadlock” buildings
• Draw multi-layer structures for Condo/commercial/industrial & dense building block. Use “brother” method to draw quickly and correctly.

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The end