how to create a square buffer around a point feature

[Dahram A.]

Dear MapInfo User,

Please help, how to create a square buffer around a point feature in MapInfo Pro ver. 21 ?

Regards,

Dahram A.

[Peter Horne]

Hi Dahram,

Note  I am using V23, but pretty sure this should work in V21 as well

When using the buffer function change the number of segments to 4. See attached images.

Hope this helps.

Thx Peter 

[Peter Horne]

Haven't played much with AI , but thought I would see what CHATGTP would come up with as answer to this problem. Interesting....

mapbasic program to draw square around a point

Chatgtp said:

Perfect — you want the square centered on a point rather than giving fixed coordinates. In MapBasic you can take a point’s X and Y, then compute the corners of the square from that center. Here’s a working example:

' Program: DrawSquareAroundPoint.mbx ' Purpose: Draw a square polygon around a given point 

 Include "mapbasic.def" Declare Sub Main Sub Main Dim x As Float, y As Float Dim halfSide As Float ' Example point coordinates x = 500 ' X coordinate of the point y = 500 ' Y coordinate of the point ' Half the side length of the square halfSide = 50 ' Create a table to store the square Create Table SquareTable ( ID Integer, obj obj ) File "SquareTable.TAB" Open Table "SquareTable" ' Insert square polygon centered on (x,y) Insert Into SquareTable (ID, obj) Values (1, CreatePolygon( _ x - halfSide, y - halfSide, _ x + halfSide, y - halfSide, _ x + halfSide, y + halfSide, _ x - halfSide, y + halfSide, _ x - halfSide, y - halfSide)) ' Add layer to current map Add Map Layer SquareTable End Sub

How it works:

• (x,y) is your point.

• halfSide controls the size of the square (so side length = 2 * halfSide).

• The square is built by offsetting the point’s coordinates.

• The polygon is explicitly closed by repeating the first coordinate at the end.

👉 Do you want this program to take the point from an existing MapInfo table (e.g., you click a point on the map), or is a fixed coordinate good enough?

[Uffe Kousgaard]

Hi,

Interesting yes, but it also doesn't compile.
1) You can not create a field called obj as part of create Table
2) There is no CreatePolygon function
3) Strange _ in the function call before the x values.

Here is an adapted version, which works. The MBR hack is from Peter Møller.

' Purpose: Draw a square polygon around a given point 
Include "mapbasic.def"

Declare Sub Main

Sub Main
Dim x As Float, y As Float
Dim halfSide As Float

' Example point coordinates

x = 50

' X coordinate of the point

y = 50

' Y coordinate of the point

' Half the side length of the square

halfSide = 1

' Create a table to store the square

Create Table SquareTable ( ID Integer) File "SquareTable.TAB"
Open Table "SquareTable"
Create Map for SquareTable

' Insert square polygon centered on (x,y)

Insert Into SquareTable (ID, obj) Values (1, MBR(CreateLine( x-halfSide, y-halfSide,x+halfSide, y+halfSide)))

' Add layer to current map
Add Map Layer SquareTable

End Sub 

Kind regards
Uffe Kousgaard

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[Dahram A.]

Hi Peter,

Thank you for your help.  

It works.  I make a 45 degree rotation to fix square position.

Regards,

Dahram A.

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[Dahram A.]

Hi Uffe,

Thank you for your answer. 

Regards,

Dahram A.

To view this discussion visit https://groups.google.com/d/msgid/mapinfo-l/4d9af376-418c-4ab4-bf31-672c4496bc2b%40routeware.dk.

[Peter Horne]

Yeah Uffe, I realised it wouldn't compile, but AI will "refine" the result by telling it what errors you encounter when compiling. Probably will never give the absolute correct answer but gives a reasonable bag of bones to put some flesh on, if you don't know where to start. Won't ever replace expert knowledge though