Unexpected third layer in GemPy model despite mapping only two formations

[ajndekker]

**What is your question?**I'm working with GemPy 3 to build a simple geological model with two formations: Limestone and basement. My input data is minimal — just one orientation point per formation, and several surface points for each.

However, when I use ImporterHelper, GemPy creates three layers instead of two. Specifically, I end up with two separate "basement" layers, each with a different color. This seems to happen automatically during model creation.

🔧 Code

import gempy as gp
import gempy_viewer as gpv
import pandas as pd

# Load data
surface_df = pd.read_csv('/content/surface_points.csv')
orientation_df = pd.read_csv('/content/orientations.csv')

# Create model using ImporterHelper
geo_model = gp.create_geomodel(
    project_name='GeoModel_NL_Biesbosch',
    extent=[0, 780, -200, 200, -582, 0],
    resolution=(50, 50, 50),
    importer_helper=gp.data.ImporterHelper(
        path_to_surface_points='/content/surface_points.csv',
        path_to_orientations='/content/orientations.csv'
    )
)

# Map surfaces to series
gp.map_stack_to_surfaces(
    gempy_model=geo_model,
    mapping_object={
        "Strat_Series": ("Limestone", "basement")
    }
)

# Compute model
gp.compute_model(geo_model)

# Inspect layers
for el in geo_model.structural_frame.structural_elements:
    print(f" - {el.name}, color: {el.color}")

X,Y,Z,G_x,G_y,G_z,formation
225,0,-95,0,0,1,Limestone
225,0,-200,0,0,1,basement

Problem
I expect two layers: Limestone and basement

Instead, I get three layers, with two separate entries for basement (different colors)

This only happens when using ImporterHelper. If I manually build a StructuralFrame, I get two layers — but the plot remains empty unless I manually add data.

[NilsChudalla]

Hi @ajndekker,

a "basement" is added automatically, below the last surface in the structural frame. As long as there is no acutal third surface (I do not mean colorized volume in the plot) generated, this is expected behaviour. This automatically generated basement does also not appear in the structural frame, which is a choice of design. Could you try to rename your basement surface and verify, that the default basement just appears as "basement"? If you still believe there is something wrong, please provide the data to reproduce your error :) (you can also invite me to a private repo if you do not want your model floating out here in the open)

[ajndekker]

Hi @ajndekker,

a "basement" is added automatically, below the last surface in the structural frame. As long as there is no acutal third surface (I do not mean colorized volume in the plot) generated, this is expected behaviour. This automatically generated basement does also not appear in the structural frame, which is a choice of design. Could you try to rename your basement surface and verify, that the default basement just appears as "basement"? If you still believe there is something wrong, please provide the data to reproduce your error :) (you can also invite me to a private repo if you do not want your model floating out here in the open)

thanks it solved my problem

[NilsChudalla]

Great, glad I could help! Since this was not an actual issue, I will move this to our discussion board for future reference :)