# Defining a Model Setup with Negative values for DEM

**URL:** <https://gpusph.discourse.group/t/defining-a-model-setup-with-negative-values-for-dem/220>\
**Category:** Uncategorized\
**Created:** [March 18, 2025, 12:41am UTC](https://gpusph.discourse.group/t/defining-a-model-setup-with-negative-values-for-dem/220 "2025-03-18T00:41:57Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![AlirezaZarei](https://avatars.discourse-cdn.com/v4/letter/a/b5ac83/32.png) [@AlirezaZarei](https://gpusph.discourse.group/u/AlirezaZarei)\
**Post date:** [March 18, 2025, 12:41am UTC](https://gpusph.discourse.group/t/defining-a-model-setup-with-negative-values-for-dem/220/1 "2025-03-18T00:41:57Z")

</div>

Hi Giuseppe,  
I hope you’re doing well.

Is it possible to define a model setup using a DEM that includes a long flume (50 m) positioned between -20 m and 30 m? I tried using negative values for “west” and “east” in my DEM file, but it didn’t work.

I’d appreciate any guidance on this.

Best regards,  
Alireza

---

<div class="post-metadata">

**Author:** ![giuseppe.bilotta](https://yyz2.discourse-cdn.com/free1/user_avatar/gpusph.discourse.group/giuseppe.bilotta/32/72_2.png) [@giuseppe.bilotta](https://gpusph.discourse.group/u/giuseppe.bilotta)\
**Post date:** [March 18, 2025, 5:59am UTC](https://gpusph.discourse.group/t/defining-a-model-setup-with-negative-values-for-dem/220/2 "2025-03-18T05:59:04Z")

</div>

Hello @AlirezaZarei,

the DEM file is always imported with the corner at (0, 0). You should then be able to use `shift()` to change its offset in world coordinates. Something like:

```auto
GeometryID dem = addDEM(....);
shift(dem, -20, 0, 0); // values are the offsets in X, Y and Z direction

```

---

<div class="post-metadata">

**Author:** ![AlirezaZarei](https://avatars.discourse-cdn.com/v4/letter/a/b5ac83/32.png) [@AlirezaZarei](https://gpusph.discourse.group/u/AlirezaZarei)\
**Post date:** [March 24, 2025, 9:34pm UTC](https://gpusph.discourse.group/t/defining-a-model-setup-with-negative-values-for-dem/220/3 "2025-03-24T21:34:48Z")

</div>

Hi Giuseppe,

I just used `shift()` and it worked properly. Thanks!

Alireza