---
title: "Area calculation using vertices"
url: "https://openforis.support/questions/1499/area-calculation-using-vertices"
tags: ["collect"]
status: "answered"
score: 0
answer_count: 2
asked: "2017-12-02T14:23:10"
last_activity: "2017-12-04T12:48:30"
source: "Open Foris Support - Q&A Forum"
license: "Copyright Open Foris, 2026. Some rights reserved under creative commons license."
---

# Area calculation using vertices

Asked by Rajkumar on 2017-12-02

Hi OFT,
I am trying to develop a form that will survey of particular forest area and the forest user group territory. It would be worthy when user can get instant area he/she surveyed and make decision instantly with forest user group.I want to calculate the area in collect mobile (SRS system will be projected). For this I need to calculate x1 * y2. I thought it will be easier using idm:position() or idm:index() function but I was wrong. Now things are being messy. How can be done such type of calculation? or is their any solution to calculate area using vertices?


## Answer (score 0, by Rajkumar on 2017-12-02)

Link: https://openforis.support/questions/1499/area-calculation-using-vertices/1500

I solved one issue: x1*y2 using expression	**(location/@x*(parent()/coordinate[idm:position($this/parent()) -1]/location/@y))-(location/@y*(parent()/coordinate[idm:position($this/parent()) - 1]/location/@x))
Apply when idm:position($this/parent()) = 1
expression	(location/@x*(parent()/coordinate[idm:position($this/parent()) -1]/location/@y))-(location/@y*(parent()/coordinate[idm:position($this/parent()) - 1]/location/@x))
Apply when	idm:position($this/parent()) !=1**. probably my apply when condition is not ok, I am not sure. I checked in excel everything is right. Now my problem is that I want same calculation as above but that would be with last and first position of the coordinate. How can I perform that work?


## Answer (score 0, by Rajkumar on 2017-12-04)

Link: https://openforis.support/questions/1499/area-calculation-using-vertices/1502

Hi all,
I am able to calculate area using vertices somehow. It can be calculate in desktop version but not in mobile version. I am waiting whether it will be done in future releases in mobile. Thank you.