diff --git a/IFCGeoRefCheckerGUI/ValueConverters/InputValidations.cs b/IFCGeoRefCheckerGUI/ValueConverters/InputValidations.cs
new file mode 100644
index 0000000..e6786ee
--- /dev/null
+++ b/IFCGeoRefCheckerGUI/ValueConverters/InputValidations.cs
@@ -0,0 +1,172 @@
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.ComponentModel;
+using System.Globalization;
+using System.Linq;
+using System.Runtime.CompilerServices;
+using System.Text;
+using System.Threading.Tasks;
+using System.Windows;
+using System.Windows.Controls;
+using System.Windows.Data;
+using System.Windows.Media;
+
+namespace IFCGeoRefCheckerGUI.ValueConverters
+{
+    public class LatLonRule : ValidationRule
+    {
+        public double Min { get; set; }
+        public double Max { get; set; }
+
+        public LatLonRule()
+        {
+
+        }
+
+        public override ValidationResult Validate(object value, CultureInfo cultureInfo)
+        {
+            double angle = 0.0;
+
+            try
+            {
+                if (((string)value).Length > 0) { angle = Double.Parse((string)value, cultureInfo); }
+            }
+            catch (Exception e)
+            {
+                return new ValidationResult(false, $"Illegal characters or {e.Message}");
+            }
+
+            if ((angle < Min) || (angle > Max))
+            {
+                return new ValidationResult(false, $"Please enter an decimal angle between {Min} and {Max}");
+            }
+            return ValidationResult.ValidResult;
+        }
+    }
+
+    public class InputValidator
+    {
+        public static bool IsValid(DependencyObject parent)
+        {
+            /*
+            return !Validation.GetHasError(parent) &&
+                LogicalTreeHelper.GetChildren(parent).OfType<DependencyObject>().All(IsValid);
+            
+            
+            bool valid = true;
+
+            LocalValueEnumerator localValues = parent.GetLocalValueEnumerator();
+            while (localValues.MoveNext())
+            {
+                LocalValueEntry entry = localValues.Current;
+                if (BindingOperations.IsDataBound(parent, entry.Property))
+                {
+                    Binding binding = BindingOperations.GetBinding(parent, entry.Property);
+                    foreach (ValidationRule rule in binding.ValidationRules)
+                    {
+                        ValidationResult result = rule.Validate(parent.GetValue(entry.Property), null);
+                        if (result!.IsValid)
+                        {
+                            BindingExpression expression = BindingOperations.GetBindingExpression(parent, entry.Property);
+                            System.Windows.Controls.Validation.MarkInvalid(expression, new ValidationError(rule, expression, result.ErrorContent, null));
+                        }
+                    }
+                }
+            }
+
+            /*for (int i = 0; i != VisualTreeHelper.GetChildrenCount(parent); ++i)
+            {
+                DependencyObject child = VisualTreeHelper.GetChild(parent, i);
+                if (!IsValid(child)) { valid = false; return valid; }
+            }*/
+            bool valid = true;
+
+            LocalValueEnumerator localValues = parent.GetLocalValueEnumerator();
+            while(localValues.MoveNext())
+            {
+                LocalValueEntry entry = localValues.Current;
+                if (BindingOperations.IsDataBound(parent, entry.Property))
+                {
+                    Binding binding = BindingOperations.GetBinding(parent, entry.Property);
+                    if (binding.ValidationRules.Count > 0)
+                    {
+                        BindingExpression expression = BindingOperations.GetBindingExpression(parent, entry.Property);
+                        expression.UpdateSource();
+
+                        if (expression.HasError)
+                        {
+                            valid = false;
+                        }
+                    }
+                }
+            }
+
+            System.Collections.IEnumerable children = LogicalTreeHelper.GetChildren(parent);
+            foreach (object obj in children)
+            {
+                if (obj is DependencyObject)
+                {
+                    DependencyObject child = (DependencyObject)obj;
+                    if (!IsValid(child)) 
+                    { 
+                        return false; 
+                    }
+                }
+            }
+
+            return valid;
+            //*/
+        }
+    }
+    
+
+    public class ValidationHelper: INotifyDataErrorInfo
+    {
+        readonly IDictionary<string, List<string>> errorList = new Dictionary<string, List<string>>();
+
+        public string this[string propertyName]
+        {
+            get
+            {
+                if (errorList.ContainsKey(propertyName))
+                {
+                    return errorList[propertyName].First();
+                }
+                return String.Empty;
+            }
+        }
+
+        public bool HasErrors => errorList.Count > 0;
+
+        public event EventHandler<DataErrorsChangedEventArgs>? ErrorsChanged;
+
+        public void ClearError([CallerMemberName] string property = "")
+        {
+            if (errorList.Remove(property))
+            {
+                ErrorsChanged?.Invoke(this, new DataErrorsChangedEventArgs(property));
+            }
+            
+        }
+        public void AddError(string errorMessage, [CallerMemberName] string property = "")
+        {
+            if (!errorList.ContainsKey(property))
+            {
+                errorList.Add(property, new List<string>());
+            }
+            errorList[property].Add(errorMessage);
+        }
+
+        public IEnumerable GetErrors(string? propertyName)
+        {
+            if (errorList.ContainsKey(propertyName!))
+            {
+                return errorList[propertyName!];
+            }
+            return Array.Empty<string>();
+        }
+
+    }
+
+}
diff --git a/IFCGeoRefCheckerGUI/ValueConverters/Level20UI.cs b/IFCGeoRefCheckerGUI/ValueConverters/Level20UI.cs
new file mode 100644
index 0000000..81860b4
--- /dev/null
+++ b/IFCGeoRefCheckerGUI/ValueConverters/Level20UI.cs
@@ -0,0 +1,42 @@
+using IFCGeoRefCheckerGUI.ViewModels;
+using System;
+using System.Collections.Generic;
+using System.ComponentModel;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace IFCGeoRefCheckerGUI.ValueConverters
+{
+    public class Level20UI : BaseViewModel
+    {
+        public double? Latitude { get; set; }
+        private double? longitude;
+        public double? Longitude
+        {
+            get => longitude;
+            set
+            {
+                if (longitude != value)
+                {
+                    ValHelper.ClearError();
+                    
+                    if (value < -180.0 || value > 180.0)
+                    {
+                        ValHelper.AddError("Longitude must be between -180.0 and 180.0 degrees");
+                    }
+                    longitude = value;
+                    this.RaisePropertyChanged(nameof(Longitude));
+                    
+                }
+            }
+        }
+        public double? Elevation { get; set; }
+
+        public string? GUID { get; set; }
+
+        public ValidationHelper ValHelper { get; } = new ValidationHelper();
+        public bool HasErrors => ValHelper.HasErrors;
+
+    }
+}
diff --git a/IFCGeoRefCheckerGUI/ValueConverters/LevelsConverter.cs b/IFCGeoRefCheckerGUI/ValueConverters/LevelsConverter.cs
index c51239b..7824475 100644
--- a/IFCGeoRefCheckerGUI/ValueConverters/LevelsConverter.cs
+++ b/IFCGeoRefCheckerGUI/ValueConverters/LevelsConverter.cs
@@ -6,6 +6,7 @@
 using System.Linq;
 using System.Text;
 using System.Threading.Tasks;
+using Xbim.Ifc4.Interfaces;
 
 namespace IFCGeoRefCheckerGUI.ValueConverters
 {
@@ -34,6 +35,18 @@ public static Level10UI convertToLevel10UI(Level10 lvl10)
             return lvl10UI;
         }
 
+        public static Level20UI convertToLevel20UI(Level20 lvl20)
+        {
+            var lvl20UI = new Level20UI();
+
+            lvl20UI.Latitude = lvl20.Latitude;
+            lvl20UI.Longitude = lvl20.Longitude;
+            lvl20UI.Elevation = lvl20.Elevation;
+            lvl20UI.GUID = lvl20.ReferencedEntity?.GlobalId;
+
+            return lvl20UI;
+        }
+
         public static Level50UI convertToLevel50UI(Level50 lvl50)
         {
             var lvl50UI = new Level50UI();
@@ -54,6 +67,7 @@ public static Level50UI convertToLevel50UI(Level50 lvl50)
 
             return lvl50UI;
         }
+
     }